by Neil Bauman, Ph.D.
© April 2007 (latest revision January, 2015),
- What Is a Reverse-Slope (or Low Frequency) Hearing Loss?
- How Common Are Reverse-Slope (or Low Frequency) Hearing Losses?
- Causes of Reverse-Slope (or Low Frequency) Hearing Losses
- How Reverse-Slope (or Low Frequency) Hearing Losses Progress
- Characteristics of Reverse-Slope (or Low Frequency) Hearing Losses
- Hearing Testing and Reverse-Slope (or Low Frequency) Hearing Losses
- Amplification for Reverse-Slope (or Low Frequency) Losses
- Support List for Reverse-Slope Losses
- Literature Cited
- End Notes
Imagine a person with a hearing loss so severe he can’t hear thunder rumbling overhead, yet, at the same time, has hearing so acute he can hear a pin drop; or imagine a person that can’t hear you talking just 4 feet away, yet clearly hears a whisper from across a large room; or imagine a person that can’t hear a car motor running right beside him, yet can hear a single dry leaf skittering along in the gutter 50 feet away.
“Impossible,” you say, “a person could never have such good and bad hearing at the same time!”
What Is a Reverse-Slope (or Low Frequency) Hearing Loss?
Hearing losses are sometimes classified according to the shape they form on an audiogram. They commonly go by strange names such as ski-slope loss, cookie-bite loss, flat loss, reverse cookie-bite loss and reverse-slope (or reverse curve) hearing loss. (My article Kinds of Hearing Losses explains these different hearing losses and illustrates the various shapes they form on audiograms.)
By far the most common kind of hearing loss is the typical ski-slope loss where the line on the audiogram slopes downto the right. In contrast, a reverse-slope loss (as its name implies) does the reverse and slopes up to the right.
As a result this kind of hearing loss is sometimes referred to as an up-sloping loss, a rising loss, or even a low frequency hearing loss, but by far the most common name is the reverse-slope (or reverse curve) hearing loss.
Don’t make the mistake of thinking that all reverse-slope losses are the same. Nothing could be further from the truth. There is an enormous difference in hearing between a mild gently-sloping reverse-slope hearing loss, and a severe or profound steeply-sloping reverse-slope loss.
For practical purposes, we can group reverse-slope hearing losses into three basic classes.
Class 1. Perhaps the most common form of this relatively-rare loss is a gently up-sloping line in the standard audiometric frequencies between 250 and 8,000 Hz (Fig. 1). In this class, the worst low-frequency hearing loss typically lies somewhere between mild and moderately-severe.
Ella’s hearing fits this class. Her audiogram shows a 40 dB loss at 250 Hz sloping up to around 25 dB at 1,000 Hz and reaching 10 dB by 4,000 Hz (Fig. 1).
Diane has a bit worse reverse-slope loss. Her hearing loss ranges from 50 dB at 500 Hz to 20 dB at 4,000 Hz (Fig. 2): Diane’s mild reverse-slope loss).
Class 2. Rarer, is a fairly-steep up-sloping line in the standard audiometric frequencies. In this class, there is a moderate to severe hearing loss in the frequencies below 1,000 Hz, but at the same time, hearing becomes virtually normal somewhere in the range of 2,000 to 6,000 Hz (Fig. 3: Severe reverse-slope loss).1
Lorene’s hearing loss falls into this category. She explains, “The audiogram for my right ear starts at 90 dB at 250 Hz and rises to 30 dB at 8000 Hz.”
Class 3. The rarest form of the reverse-slope loss reveals a steep up-sloping line ranging from 70 to 110 dB in the low frequencies to incredible “dog-ears” hearing in the very high frequencies (those frequencies above 8,000 Hz) (Fig. 4: Neil”s extreme reverse-slope loss).
Years ago when I was around 20, my hearing ranged from 75 dB at 1,000 Hz to -30 dB above 16,000 Hz (Fig. 4). (Note: numbers above the 0 dB line represent super-acute hearing, and are expressed as negative numbers.) Hearing at -30 dB means you can hear sounds so faint that people with normal (perfect) hearing can’t hear them at all. In fact, my very high frequency hearing (well above 10,000 Hz) was at one time so sensitive that the energy needed to produce the faintest sound I could hear needed to be multiplied 1,000 times before a person with “perfect” hearing could even begin to hear it! That’s some incredible hearing. Since I could easily hear “silent” dog whistles, some said I had “dog ears” hearing.
Reverse-slope hearing losses give rise to various degrees of “weird” hearing. This is caused by two main factors. The first factor is the amount (degree) of hearing loss we have in the low frequencies. This indicates what sounds we will not hear. For example, if we have severe or worse low-frequency hearing losses, we will not hear common loud sounds such as thunder, car and truck motors running, fans whirring, and the speech sounds that give speech most of its volume and fullness.
The second factor is the difference in volume (measured in decibels) between the softest low-frequency sound we can hear and the softest high-frequency sound we can hear. The greater this range, the weirder our hearing losses become.
Notice that the total range of the reverse-slope loss in Class 1 is not all that much—somewhere in the range of 30 dB. In the previous examples, both Ella’s and Diane’s hearing losses only range 30 dB between their worst and best frequencies. At this point, hearing loss is not all that strange, but people with these losses begin to exhibit some of the characteristics of those with more severe reverse-slope losses.
In Class 2 the range increases dramatically to somewhere between 60 and perhaps 90 dB, and with this increased range, there is a marked increase in the degree of hearing loss “weirdness.” Notice that Lorene’s hearing loss has a range of 60 dB.
However, it is in Class 3, with its incredible range of over 100 dB between the faintest low-frequency sound heard and the faintest high-frequency sound heard that truly bizarre hearing is the most pronounced. My hearing loss spanned an incredible range of 105 dB. No wonder people were always confused about what I could, and could not, hear!
Incidentally, since hearing is normally only tested to 8,000 Hz (because the typical audiometers in use today are only calibrated to 8,000 Hz), an audiogram of people with incredible high-frequency hearing gives a false impression of what that person really hears. In fact, people with my kind of hearing loss have been sent to “shrinks” because the medical professionals were so sure they were lying about what they could hear!
Therefore, if a person has a Class 2 or 3 reverse-slope loss, it is imperative that their hearing be tested to at least 16,000 Hz. (and preferably to the highest frequency they can hear), and to the softest sound they can hear, in order to properly diagnose their reverse-slope loss.
How Common Are Reverse-Slope (or Low Frequency) Hearing Losses?
Reverse-slope hearing losses are not common. Most people with reverse-slope losses tend towards the milder form, but I have run across a few people with severe to extreme forms like mine.
In fact, significant reverse-slope hearing losses like mine are very rare. Out of roughly 38 million hard of hearing people in the USA and Canada, only about 3,000 of us have this unusual hearing loss according to Dr. Charles Berlin, formerly the head of the Kresge Institute in Louisiana, one researcher that has studied this kind of hearing loss fairly extensively.
This means that only one person out of every 12,000 hard of hearing people has a significant reverse-slope loss. No wonder hearing health care professionals seldom see such cases. Consequently, there is little authoritative information written on this subject.
Causes of Reverse-Slope (or Low Frequency) Hearing Losses
There are a number of causes of reverse-slope losses, but the two most common causes seem to be certain genetic (hereditary) abnormalities and Meniere’s Disease.
When people think of causes of reverse-slope losses, typically they think about Meniere’s disease. Classic Meniere’s disease does indeed often, but not always, result in a reverse-slope hearing loss, at least in the beginning stages. From what I have seen, reverse-slope losses due to Meniere’s Disease tend to be more of the Class 1 kind of curve.
Probably the most common cause of reverse-slope hearing losses, particularly in Classes 2 and 3, is of genetic origin. Hereditary losses seem to run in our families more often than not. For example, Dolores explained, “I think my reverse-slope hearing loss is genetic. My mother and sister have it too.”
Reverse-slope hearing loss runs in my family—at least it has for the past five generations. Those that I know of include my maternal grandfather, my mother, myself, my brother, my younger daughter and my brother’s older son and his son. My hearing loss is the worst in the tribe, with my daughter’s poor hearing coming in a close second. In addition, I know of other people who also have reverse-slope hearing losses running in their families—at least for the past 4 or 5 generations.
From the above, it appears that extreme reverse-slope hearing losses are a dominant genetic trait. It certainly is in my family. Each person born in my family has a 50% chance of having this kind of hearing loss.
In contrast, most other cases of genetic hearing loss seem to stem from recessive genes. In such cases, there is only a 25% chance of each child having a hearing loss (although there is a 50% chance of any child being a carrier, but not having a hearing loss). Furthermore, if the hearing loss is caused by a recessive gene, it may appear to skip several generations. This is because in order for it to show up, both parents have to be carriers of the same recessive gene.
Another interesting characteristic of severe or extreme reverse-slope hearing losses such as mine is that they are non-syndromic—that is, they don’t have any other conditions or syndromes associated with them. This is also in contrast to many cases of hearing loss from recessive genes where various syndromes are associated with these hearing losses.
I think many people, including doctors, stretch to find obvious causes for these hearing losses—and fail to realize that they really may be hereditary. For example, my mom was knocked down and run over by a street car when she was 5 or 6. When they noticed that she had poor hearing after that, they attributed it to the head trauma she sustained in that accident—yet it is now obvious that she really had an hereditary reverse-slope loss that she passed on to me and my brother.
Various childhood diseases are also thought to sometimes result in reverse-slope hearing losses. For example, Debbie wrote, “I acquired my loss from a rare illness when I was four years old. My daughter also shares my type of loss, although it has never been concluded that it is genetic in nature. Like me, she was not born with a hearing loss but acquired it from complications of chicken pox at age 2. The complications led to the same serious disease that I had when I was four.”
Judith explained, “My hearing loss apparently was the result of measles at the age of 2. My audiologist says I have reverse-slope hearing loss.”
How Reverse-Slope Hearing (or Low Frequency) Losses Progress
Whether reverse-slope losses get worse with time depends on what caused the loss in the first place. In general, it doesn’t seem that reverse-slope losses progress much differently from other kinds of hearing losses with two notable exceptions.
One of the characteristics of Meniere’s Disease is that it results in a progressive, fluctuating step-wise hearing loss. Thus if you have Meniere’s Disease, initially you may have a Class 1 type of reverse-slope loss. Over time, as your Meniere’s Disease progresses, you will likely find that this reverse-slope loss slowly evolves into a reverse cookie-bite or flat loss and ultimately into some degree of a severe or profound ski-slope loss.
With hereditary reverse-slope losses, we seem to go through three distinct stages.
Stage 1: The first stage occurs from birth to around 5 years of age. It appears that although there is some degree of hearing loss at birth, hearing in the lower frequencies rapidly decreases until around age 5 or so.
When my daughters were born, we were expecting one of them to be hard of hearing. Thus, we carefully observed them from birth in order to watch for any developing hearing loss. As a result, my hard of hearing daughter had several audiograms in her early childhood years which documented her increasing hearing loss from birth to age 5.
Furthermore, it seems that because of our excellent high-frequency hearing and because of our good speechreading skills at a very early age (of which our parents are typically totally unaware), our hearing losses do not become apparent until something traumatic happens as was the case with my mother (mentioned above), or something happens to drive home the fact that we cannot hear well.
For example, my parents didn’t discover I had a hearing loss until I was about 4 or 5. One day my dad, who was standing behind me where I couldn’t speechread him, asked, “Do you want to come for a ride in the car with me?” I totally ignored him, and continued playing on the floor. He knew something was wrong because I loved riding in the car! (It was a ‘29 Buick in those days.) Another time he asked me if I wanted some ice cream—which I still love—and again I ignored him. It was at this point that my parents had my hearing tested and discovered I had a severe hearing loss!
Stage 2: The second stage goes from about age 5 to around age 50 (if there are no other factors involved such as hearing loss from noise damage or from taking ototoxic drugs, for example).
The good news is that in stage 2, hearing loss doesn’t change much if at all. It remains stable through childhood, and early and middle adulthood. Debbie explained, “My hearing has for the most part, remained stable for as long as I can remember.” This has been my experience too, and my mother’s and daughter’s experience as well.
Thus, once we learn to adapt to our strange hearing losses, our coping strategies can remain the same for most of our lives.
Stage 3: The third stage kicks in about age 50 and continues for the rest of our lives. This is not really our reverse-slope hearing loss progressing, but rather, the effects of aging dramatically impinging on our precious high-frequency hearing. Here’s what happens.
As people age, they typically begin to lose their high-frequency hearing. This happens slowly and insidiously over many years. Fig. 5 plots “average” curves showing increasing high-frequency hearing loss from ages 40 (top line) to age 80 (bottom line).
The fact that people normally lose much of their high-frequency hearing as they age has some important ramifications for those of us with reverse-slope losses.
Notice that people with the typical ski-slope losses have already lost their high-frequency hearing (but retain their low-frequency hearing). Thus as they age, they don’t have much high-frequency hearing left to lose.
In contrast, those of us with extreme reverse-slope losses have most of our residual hearing in the high (and very high) frequencies, yet it is these very frequencies that people typically lose as they get older. As a result, somewhere around age 50 or so we begin to notice a significant drop in our hearing. Our reverse-curve loss rapidly begins to flatten and in time becomes more or less a flat curve.
For example, between age 50 and age 60, I lost a lot of my excellent high-frequency hearing. As a result, I don’t hear much at all any more—but this is the result of aging, rather than from a progressive reverse-slope hearing loss.
To verify this, compare my audiogram taken at around age 21 (Fig. 4) with my current audiogram (Fig. 6) taken at age 59. As you can see, I have lost much of my high-frequency hearing. I no longer hear many of the familiar high-frequency sounds I used to depend on. Now I am having to learn other coping skills to make up for this loss. My world is rapidly becoming more and more silent. Eventually, if I follow my mother’s pattern, I’ll probably have a flat “curve” at around 80 dB or so.)
Characteristics of Reverse-Slope (or Low Frequency) Hearing Losses
What It’s Like to Live with a Reverse-Slope Hearing Loss
Having a Class 2 or 3 reverse-slope loss makes for some interesting experiences. Here are some of the things that we hear, or don’t hear, and how we cope with it.
- We don’t hear normal sounds that tell us that certain appliances are running. For example, I have to put my hand on some of my household appliances and feel the vibrations in order to know if they are running, or watch them for movement. Furthermore, I can’t hear the low-frequency hum of the furnace, fridge, washer, drier, dishwasher, etc. so, likewise, in order to know if they are running, I have to put my hand on them (or look at the dials). However, the interesting thing is that we can easily hear the faint clicks of the relays kicking in/out to start/stop all these appliances. Thus, we can tell when they start or stop—we just don’t know whether they just started or just stopped. Lorene echoes my experiences when she explains, “I can hear the fridge kicking in, but can’t hear it when it is running.”
- When hard of hearing people get together in a room, those with ski-slope hearing losses complain how the noisy heating and air conditioning systems drown out speech, yet, without our hearing aids, we don’t even know these devices are making sounds at all!” These sounds certainly don’t bother us!
- In noisy conditions such as in mills and manufacturing plants, hearing people have to shout over all the low-frequency noise around them. Since we don’t hear low-frequency sounds well, we clearly hear the people shouting. That’s the one situation where I tell people (tongue in cheek), “You don’t have to yell at me. I’m not deaf!”
- Since loud low-frequency sounds mask softer high-frequency sounds, and since we don’t hear low-frequency sounds well, the softer high-frequency sounds stand out clearly to us. When we hear such soft high-frequency sounds, people think we must have incredible hearing, not that we are almost deaf. No wonder hearing people sometimes don’t think we are hard of hearing at all!
- Our hearing is exactly backwards to that of the typical hard of hearing person. As Debbie explains, “I have near normal hearing in the high frequencies, but my hearing drops off in the low and speech frequencies.” This is just the opposite of what people with ski-slope losses have. Thus most things they hear, we don’t, and most things we hear, they don’t.
- We generally can’t hear car motors running. This can make for some interesting experiences in parking lots. As a result, we need to use our eyes and watch for back-up lights and/or brake lights coming on if we are walking behind cars, or watch for their driving lights coming on if we are in front of them.
- Since I can’t hear my car’s motor running, sometimes when I am parked I may try to start my car a second time thinking it hadn’t started. The suddenly-swiveled heads of the people nearby tell me that I just ground the gears on the starter—again! Now, since modern cars have tachometers, I always look at the tachometer first. If it’s not reading 0, I leave the starter alone!
- I hear squeaking fan belts and squealing brakes very well. Often that is all I hear of motor vehicles approaching me, or running nearby.
- The screech of the wheels of trains on the tracks is so loud to me that it hurts my ears—yet to most people this is not even a loud sound. Imagine not being able to hear the loud roar of a train bearing down on you, yet getting headaches from the painfully-loud screech (to me) of the train wheels against the tracks as the train goes around a curve. This includes modern light rail systems in most big cities.
- We don’t hear the low-frequency sounds of things like big 18-wheelers rumbling beside us, but when their air compressors bleed off with a “pshhhhhh,” that sound is so loud that it is one of the few outside sounds I can hear from inside a building.
- We can hear whispers from considerable distances. For example, in school, I used to hear kids whispering from across the classroom, yet couldn’t hear the teacher talking only a few feet away. (I always had to speechread my teachers to know what they were saying.) It always puzzled me that the teachers never heard all the whispering that to me was so loud.
- We can hear phones ringing—especially if they have the old style bells for ringers—but can’t hear people talking on them. For example, I could clearly hear the phone ringing in my mom’s house while I was standing on the far side of the highway across from her house, even though her house was set back from the road a ways, the phone was mounted on an inside wall and the doors and windows were shut. Debbie has similar hearing to mine and relates, “I hear the alarm and phone ringing even when my hearing husband doesn’t!” With such incredible hearing, people can’t understand why pressing the receiver tight against our ears still doesn’t let us hear and understand the person on the other end unless we have special amplified phones.
- When it comes to using phones, we are at a decided disadvantage. You see, the high frequencies upon which we depend are deliberately chopped off to save “bandwidth.” Standard commercial phones are designed to have a flat frequency response from about 300 Hz to 3,400 Hz. After that, the frequency response drops off sharply. As a result, even when we use special amplified phones to give us the overall volume we need, we still find speech difficult to understand because the sound signal lacks the high-frequency component we so much rely on to give speech its intelligibility.
- We can easily hear sounds most people don’t hear. For example, when I was younger, I could easily hear the inaudible (to most people) 15,734 Hz whine produced by the fly-back transformer of a TV from anywhere in the house, and even from outside the house, yet I had to put my ear about 6 inches from the TV’s speaker in order to understand any speech from it (if the volume was set to normal hearing levels).
- We hear insects that other people don’t seem to hear well, if at all. To me, certain insects chirping from a block away (even just one insect) produce a racket loud enough to drown out the voice of a person standing almost nose-to-nose speaking to me. The “funny” thing (to me) is that people with normal hearing either can’t hear that insect at all, or only hear it very faintly!
- We hear some birds singing and chirping away, but not others. For example, I have never heard the low-frequency sounds of an owl hooting or a Mourning Dove cooing (although I have a flock of Mourning Doves right outside my back door). I cannot hear a large flock of geese honking overhead, unless they are flying almost at ground level, yet I can easily hear a male hummingbird’s high-pitched angry squeaks as it chases off a competitor, or the wonderful trilling sounds it makes as it power dives to impress its prospective mate.
- Water running in the sink typically drowns out any speech for us. We have to turn the water off in order to converse.
- We cannot understand what is said via public address systems. As Lorene explains, “I cannot understand any announcements in stores or malls.” This is my experience too.
- We hear women’s higher-pitched voices better than men’s lower-pitched voices—exactly the opposite of those with the more-common kinds of hearing losses.
- When inside, we do not hear traffic going by outside the house. Traffic noise definitely does not disturb our sleep!
- Road noise does not bother us much, even when the windows are down.
- We can hear sirens if we are outside and they are close by. However, if we are in our cars or houses, we don’t hear a thing. For example, for 10 years I lived right beside the fire hall and the fire trucks could roar out with their sirens blaring and I’d not hear a thing if I was inside the house. (Since I was a fireman, it would have been a bit embarrassing if they had left without me!)
- We hear/don’t hear the strangest things. For example, I can hear a dry leaf skittering down the street from 50 feet away, but can’t hear a car motor running right beside me.
- We do not hear somebody coming up behind us on a bicycle, and, as Lorene relates, “scaring the life out of me as they whiz past.”
- We cannot hear jets flying overhead when we are outside.
- We only hear thunder when it is very loud and almost overhead. We seldom hear the rain beating on the windows—unless it is a violent storm driving the rain into the glass, or there is hail or ice in the rain. Even then, we only hear the high-frequency component of the sound hail makes when hitting the windows.
- Although we have severe hearing losses in the speech frequencies, we can easily hear faint high-frequency sounds such as a pin dropping on a table or hard floor. Sarah explains, “I have a 60-80 dB reverse-slope hearing loss. I can hear a pin drop, but normally can’t hear thunder! I’m the same. I can easily hear pins dropping, but not thunder unless it is very loud.
- We don’t hear strange noises outside. (What? You mean there are strange noises outside!) That’s like the hearing person who asked a group of us (hard of hearing people) if it bothered us when people talked about us behind our backs and we replied, “They do?”
- Sound deadening tiles deaden the higher-frequency sounds we normally hear. Thus, we find it more difficult to hear in rooms with acoustical tile since the purpose of the tile is to absorb the high-frequency noises most people find annoying, but to us are critical to understanding what we are hearing.
- Adjusting the treble on a radio or stereo changes the volume for us. As strange as it my seem, for years I couldn’t tell much difference between the treble control and the volume control on a radio or stereo. Turning up the treble made the sound louder, just like turning up the volume control did. I can remember when my wife would turn on the radio, and if it was bothering me I’d just turn down the tone until I couldn’t hear it—and both of us were happy. (I could also precisely tune (zero-beat) a radio to an FM station I couldn’t even hear. I would just tune it for no “hiss” or “whistle” and when it was in perfect tune, I couldn’t hear a thing! My wife could never do that with her normal hearing.
Reverse-Slope Losses vs. Ski-Slope Losses
There are some very real differences between how we perceive speech as compared to how people with ski-slope losses hear speech. Naturally, the worse our hearing is, the more pronounced these differences become.
These differences are largely the result of the following 6 basic facts concerning speech and hearing. I think you will find this very enlightening.
- Speech is composed of vowels and consonants. Vowels are loud sounds while consonants generally are softer sounds. In fact, roughly 95% of speech energy goes into producing the 5 vowel sounds. This means that only 5% of speech energy is left to produce the 21 remaining consonants.
- Vowels basically produce lower-frequency sounds, while many consonants produce higher-frequency sounds.
- Most of the volume of speech comes from the (lower-frequency) vowels.
- Most of the intelligibility of speech is contained in the (higher-frequency) consonants. Thus, to a large extent, vowels give speech its volume, while consonants give speech its intelligibility. You can easily prove this. Write out a sentence, then take out all the vowels leaving blanks—and show it to someone, and they, with a bit of reflection, will be able to fill in the blanks and read the sentence correctly. Now try the same sentence, but with all the consonants removed. The sentence is impossible to decipher. If you tried pronouncing it, all you would hear is something akin to an Indian chant or war-cry.
- Low-frequency sounds travel considerable distances in air.
- High-frequency sounds are quickly attenuated in air so they don’t travel very far.
Now let’s put all these facts together and see exactly what it means to those of us with reverse-slope losses as opposed to those with the common ski-slope losses. Many of the coping skills you read about are for people with ski-slope losses, not for those of us with reverse-slope losses.
1. If you have a ski-slope loss you hear the loud vowel sounds, but not the soft consonants. Thus you hear people talking with no problem, but because most of the intelligence of speech is in the consonants, you don’t understand what people are saying. To you, speech sounds muffled because you don’t hear the high-frequency sounds. Thus you want more clarity.
In contrast, those of us with reverse-slope losses hear the soft high-frequency consonant sounds. Thus speech is thin, almost inaudible and often sounds like whispers. For example, as I approach someone talking, the first sounds I hear are the high-frequency voiceless “s” sounds. This is how I know someone is talking. We do not really hear a person talking until we get very close so we can hear the “voiced sounds.” Fortunately, we generally understand speech when it is finally loud enough for us to hear it. Thus we typically need more volume.
One of the “rules” when speaking to a hard of hearing person (really meaning those with ski-slope losses) is that you do not “yell” at them, but speak in a normal volume. Since they need clarity, not more volume, they want you to speak at a normal level, but speak slowly and clearly to enable them to catch the high-frequency consonantal sounds as best they can.
This approach is totally wrong for those of us with reverse-slope losses. We need people to speak louder in order to hear speech in the first place because we do not hear the low-frequency sounds that give speech much of its volume.
2. If you have a ski-slope loss, you can hear people talking from a considerable distance because low-frequency vowel sounds travel well in air. As a result, you can hear a person calling to you from a distance. Thus, you would turn around at a shouted warning (to see what the racket was about).
However, those of us with reverse-slope losses cannot hear people until we are almost nose-to-nose with them because we don’t hear the vowel sounds that give speech its volume and ability to travel far in air. As a result, we don’t hear people calling to us from any distance at all, so we often do not respond to shouted warnings.
3. Another bit of “common wisdom” is that hard of hearing people hear men better than women and children. This is true for people with the typical ski-slope losses because they hear the louder, lower-pitched voices of men better since they hear low-frequency sounds best. Women and children with their higher-pitched (and often softer) voices are much more difficult for them to hear and understand.
This “wisdom” is also totally wrong for those of us with reverse-slope losses. Since we hear the higher-frequency sounds best, we typically hear women’s voices better than men’s voices. As Rusty says, “Men’s voices have been difficult for me to hear.” I, too, much prefer talking to women as their voices are higher pitched and more in tune with my ears. Their high soprano voices are so lovely for me to hear and understand. Debbie explains, “I do not use the phone unless it is someone I can understand, namely a high-pitched female voice.”
Unfortunately for us, women don’t put as much sound energy into their voices as men do. Thus, we can’t hear them from any distance, but close up they are so easy to hear and understand. As a result, I normally stand almost nose-to-nose when I am talking to someone. I remember talking to my hard of hearing friend Elizabeth. We were out in the middle of a big, almost-empty arena—yet we were standing there nose-to-nose enjoying our chat.
4. People with ski-slope losses can’t hear whispers. Surprisingly enough, those of us with reverse-slope losses hear whispers very clearly—even from across a room. My former mother-in-law wouldn’t believe my hearing was as bad as it was because she would whisper when she didn’t want me to hear something, and I would hear her. (She never got it through her head that if she just spoke in a normal voice, I wouldn’t have understood a thing!)
To me, whispering seemed quite loud, so when I used to “whisper,” I’d actually use “low voice” (which to me sounded very faint as compared to whispering). To my chagrin, everyone around me heard me “whispering.” My wife kept telling me to “whisper.” It eventually dawned on me that others couldn’t hear the whispers I so easily heard.
5. If you have a ski-slope loss, you can’t hear in the presence of low-frequency noise.
In contrast, we typically hear better in “noisy” situations (if the noise is all low-frequency sounds) because we don’t hear these louder low-frequency sounds much, and people in noise tend to speak up (or shout) in such situations. Since we need more speech volume anyway, this is exactly what we need in order to hear.
Because people with normal hearing lower their voices in quiet situations so much that they are inaudible to me, I use a sneaky trick to “force” them speak up. For example, if I am outside mowing the grass or rototilling the garden and someone wants to talk to me, I generally leave the motor on—just idling—so they have to speak up (over the noise). That way I can then hear them much better. I discovered that if I turned the motor off, they would lower their voices and I couldn’t hear them at all. This is just one of the tricks I use to cope with my weird hearing loss.
6. A person with a ski-slope loss can hear a car or truck approaching from a distance because they hear the low-frequency sounds of the motor. For example, I was once talking with a hard of hearing farmer with the typical high-frequency hearing loss. He heard a truck approaching while it was still half a mile down the road and turned to see who was coming. In contrast, I never heard a sound even when the truck turned into the farm yard and stopped right in front of me!
Since we don’t hear low-frequency sounds, being around moving vehicles can be dangerous to us. Thus, we have to rely on our eyes. Furthermore, we can’t rely on our ears alone when crossing roads. Crossing streets is particularly dangerous for us when it is foggy and we neither can see nor hear vehicles approaching.
7. People with ski-slope losses don’t hear high-frequency sounds, and thus aren’t bothered by them.
In contrast, high-pitched sounds may hurt our ears but not bother people with normal hearing. Thus, they discount the pain we feel from such sounds. This is particularly true for those of us who have Class 2 or 3 reverse-slope losses. Debbie explains, “Sometimes high-pitched sounds seem so loud they hurt my ears.” I have the same problem. Another lady explained, “The things that bring me out of my seat are the screaming crowds at sports games on TV and small children’s shrill voices.”
Supersensitivity to High-Frequency Sounds
Those of us with Class 3 reverse-slope losses have super-acute hearing in the very high frequencies. For example, Kathi wrote, “I used to be able to hear dog whistles, bats, and all kinds of crazy things that other people couldn’t hear. It never occurred to me that I should tell my ENT doctor about it.” Rusty related, “I hear high-pitched sounds that drive me bats—like the Celtic flute and bagpipes.” Personally, I love listening to bagpipes! (I guess it is the Scot in me.)
Paul revealed, “I could hear a watch alarm go off 100 yards away but couldn’t understand speech at all. I was supersensitive to high frequency sounds.” Grant explained, “I recall as a cub scout having someone come in with some sound equipment. One of the things he did was to try to get people to hear some really high-pitched noise. I could still hear it when all the others couldn’t. Shirley confessed, “Chirping birds drive me nuts! I also respond well to dog whistles!”
I also used to hear “silent” dog whistles and other high-frequency sounds that no one around me could hear. In fact, I had a silent dog whistle years ago—my idea was to give it to my partner when I was timber cruising—and we could communicate like that without disturbing other people around us. However, it didn’t work out in practice. First, it was so shrill to me that it gave me an instant headache. Second, since high-frequency sounds attenuate very fast in air, I couldn’t hear it from any distance at all.
Because we hear sounds that people with normal hearing can’t, it is hard for anyone to believe that we are as deaf as we are. At the same time, these high-frequency sounds may be very loud to us and hurt, and no one can understand why we are cringing, when these sounds seem normal, or faint, to them.
Music Appreciation and Reverse-Slope Losses
Another aspect of Class 2 and 3 reverse-slope hearing losses is that we experience music much differently than do people with normal hearing. For example, when listening to acoustical guitars, all I heard was the pick, pick, pick sound of the pick on the strings, not the tones the strings themselves produced. For many years, I wondered why anyone would make and play such a “stupid” musical instrument—one that didn’t even produce musical sounds!
At the other end of the music spectrum, piccolos and flutes are so shrill and thin and “hissy” that the sounds they produce sound more like fingernails screeching on a blackboard than beautiful music. This was Marge’s experience also. She explains, “I have never really enjoyed, or been able to hear, music that was pleasant to me. I hear only high tones, so ‘real music’ is all irritating and ‘screechy’.”
Since I was born with a severe reverse-slope loss, I don’t know what music really should sound like either. Even so, I love music and enjoy what little music I can hear.
However, to be really enjoyable, music has to be transposed to the octaves that make it come alive for us. For example, one lady with reverse-slope hearing loss tried a special hearing aid designed specifically to transpose low-frequency sounds to higher-frequency sounds. She reported, “So stirring was the music that suddenly I began to cry. The beauty of the sounds I was hearing was almost torture—I simply couldn’t get enough of it.”2
That is my experience too. In one church I used to attend, I once told the organist how my strange hearing only let me really enjoy music played in a certain narrow range, and with no harmony accompanying the melody. From then on, each Sunday, Ruth would transpose and play a piece at the specific pitch my ears hear best—so I too, could really enjoy the music (at least part of the time). Everyone else in the congregation thought she is just utilizing all the different voices the electric piano had—but she really did it for me. That music was so beautiful, tears would well up in my eyes, and my soul really soared listening to it.
Speech Quality and Reverse-Slope Losses
One of the things that surprises many people is that all of us with severe reverse-slope losses have perfectly-normal or near-normal speech. Imagine a person that is essentially deaf, yet has flawless enunciation, perfectly-formed and well-modulated speech, all without having had any speech therapy. This is one of the blessings of having a severe reverse-slope hearing loss.
Debbie relates, “Both my daughter Heather and I have perfect speech, which is one of the bonuses of having this strange hearing loss.” Shirley explains, “Because I have high-frequency hearing, my voice has never been affected by my hearing loss, although my hearing loss is profound.”
By perfectly-normal speech, I mean speech that is indistinguishable from the speech produced by people with normal hearing. Given the degree of our hearing losses in the speech range, you would expect us to produce the “flat” or “deaf” speech so prevalent in those with severe and profound hearing losses, but we don’t.
In a three-way study comparing the speech of people with normal hearing to people with reverse-slope losses, and to people with ski-slope losses, every person that received an “A” (excellent) for speech (meaning their speech sounded virtually as if the person had no hearing loss at all) either had normal hearing, or had considerable high-frequency hearing (hearing above 8 kHz, i.e. a reverse-slope hearing loss). In contrast, every person that received an “F” (failure) for speech had measurable hearing only in the frequencies below 3 kHz (i.e. had a ski-slope hearing loss).3
Because my speech is also indistinguishable from the speech of people with normal hearing, I’ve had many people refuse to believe how bad my hearing really is. I am talking about hearing health care professionals, not just the man on the street. It is impossible to tell that I have a hearing loss from my speech (unless, on the rare occasion, you hear me mispronounce a word that I’ve never heard spoken aloud before).
Peggy, herself hard of hearing, after hearing me speak, exclaimed, “Do you realize that your speech is absolutely perfect? You must have worked very hard to perfect your tone like that what with growing up hard of hearing.”
The surprising truth is that those of us with severe reverse-slope losses don’t need speech therapy. My perfectly-normal speech just came naturally. I’ve never had, or needed, speech therapy.
In contrast, it is a rare person that has a severe or worse ski-slope hearing loss that speaks normally. Some deaf, or profoundly hard of hearing, people do have excellent speech. In fact, I am amazed how well they speak considering they haven’t heard anything for years. For example, Hilda—totally deaf for years—has excellent speech, but it is not perfect. Her good speech comes from excellent speech memory, plus extensive speech therapy and regular “touch-up” speech therapy sessions from time to time.
All this speech therapy is not necessary for those of us with reverse-slope hearing losses. Back in 1978, Dr. Chuck Berlin realized that “one of the interesting characteristics of people with significant reverse-slope hearing losses in the severe to profound range is that they have unusually good speech. This capability has usually been attributed to post-lingual hearing loss or to unique methods of oral speech training.” However, it seems that the secret to our excellent speech is that we have good hearing in those frequencies above the traditional frequencies tested (i.e. above 8,000 Hz).4
In fact, the real secret to perfectly-normal speech is hearing all speech frequencies, especially the high-frequency consonants such as “s,” “f,” “sh,” “ch,” “t,” and “th.” These high-frequency consonants do not have any “voice.” They are simply produced by air hissing between the teeth, and around the tongue, in various ways.
When you can’t hear these sounds, it is very difficult to produce them properly. In fact, I can tell if a person is hard of hearing just by the way they move their lips when they try to produce these sounds. Think how difficult or impossible it would be to learn to whistle if you couldn’t hear any of the sounds you were trying to produce. In like manner, these voiceless sounds depend so much on aural feedback—meaning you listen to the sound you make, and if it isn’t “right on” you immediately correct it. If you cannot hear it, you don’t get this feedback so you don’t correct these sounds, and your poor speech reflects this.
Since those of us with severe reverse-slope losses hear these “voiceless” sounds the best, we use them correctly in our speech and thus avoid the flat “deaf speech” patterns of those with the typical ski-slope losses.
Let me illustrate the contrast between reverse-slope and ski-slope losses by examining the word “stop.” It is composed of 3 voiceless consonants. These consonants—“s,” “t” and “p”—are actually just air forced out of the mouth without any sound produced by the vocal cords. It contains one vowel “o” that produces vocal sound.
Breaking it down into the sounds of the individual letters, here is what actually happens.
s – air hissing between the teeth—a very high frequency sound.
t – a burst of air released from behind the teeth—another high frequency sound.
o – a loud lower-frequency vowel sound produced by the vocal cords.
p – a puff of air from the cheeks forced between the lips.
Now, if you have the typical ski-slope loss where you hear low-frequency sounds quite well, and do not hear high frequency sounds much, if at all, when someone says the word “stop” all you hear is the loud “short oh” sound “awe” and thus, that is what you repeat.
However, those of us with severe reverse-slope losses hear the voiceless sounds of the “s,” “t” and “p” and, because the “o” is a loud sound, we likely hear a bit of it too. Thus, we hear the whole word correctly—assuming it is loud enough for us to hear in the first place, otherwise we’d hear nothing. Because we hear all the sounds in the word, we also naturally produce them correctly when we speak.
Another interesting characteristic of those of us with severe reverse-slope hearing losses is that while our speech is perfectly normal, we may pitch our voices somewhat higher than normal. Thus, for example, you might think I was a baritone rather than a bass. However, when we wear properly-fitted hearing aids a surprising thing happens. Instantly our voices pitch themselves to normal.
The reason we pitch our voices higher is so we can better hear our own voices when we speak. This is a totally subconscious reflex. I have never been aware of it myself. However, people tell me that when I put my hearing aids on, the pitch of my voice drops instantly.
Dr. Berlin found the same thing in his research. Some years ago, he helped develop a special hearing aid designed specifically for those of us with severe reverse-slope losses. In one case, he noted that whenever a certain young lady wore her special hearing aid, “the fundamental frequency of her voice dropped sharply and the vowel formant frequencies became normal.” He added, “The most remarkable and consistent observation in successful users is the sudden drop in fundamental frequency of the voice, even within the first few seconds of use.”5
Hearing Testing and Reverse-Slope (or Low Frequency) Hearing Losses
Reverse-Slope Losses Often Misdiagnosed
One of the tragic characteristics of having a severe reverse-slope loss is that in the past, hearing health care professionals have often misdiagnosed us. Since ski-slope losses are so common, few hearing health care professionals realize just how differently those of us with severe reverse-slope losses perceive speech. Thus, they treat us as though we had ski-slope losses, and that is wrong!
Dr. Berlin wrote, “Virtually all of these people [with severe reverse-slope losses] have normal or nearly-normal speech, and in good listening conditions act as if they have no hearing impairment; yet with no visual cues, they sometimes appear to be quite deaf. Depending on the slope and the nature of their losses, they are among the most misdiagnosed and mismanaged hearing loss patients.”6
Such wrong diagnoses include malingering (pretending to have a hearing loss when you don’t), central hearing loss (in the brain rather than in the ears), or even normal hearing.7 Sarah wrote, “I’m fed up with having to deal with so many ignorant people who are convinced I’m faking it.”
One audiologist accused a man of lying about his hearing loss because she had not run across a reverse slope loss before. He explained, “The first audiologist I went to told me I was lying about not being able to hear. She had me take the test 3 times and was clearly frustrated with my ‘horrible lies’. To her credit, she apologized after consulting with her colleagues. It was the first time she had seen that type of loss.”
Rusty related, “I could hear the dog’s toenails on the cement walk and would tell my parents that Rex was coming. As a result, they thought my hearing was fine, and it was many years before I got my first hearing test and hearing aids.” I can relate to similar experiences with hearing the dog’s toenails clearly clicking on the floor.
Of course when you can hear a pin drop, or a whisper from across a room, and have perfectly-normal speech, it’s hard for people to believe that you have a severe hearing loss and can’t hear much at all!
Thus, sometimes, instead of believing their own audiological tests, some hearing health care professionals assume we are pretending to have a hearing loss, and thus need a “shrink.” This really happens. In fact, one lady was treated by psychiatrists and psychologists for ten years because they just assumed she had “functional hearing loss”—i.e. was faking it, before finally being diagnosed correctly as having a severe reverse-slope hearing loss.8
This was because she:
- Had a pure-tone average of 80 dB, yet had a speech detection (or reception) threshold (SRT) of only 25 dB. (Obviously if you can detect speech at 25 dB, you can’t have a loss of 80 dB—so they thought.)
- Had virtually perfect articulation of high-frequency consonants such as “s”, “sh”, “f”, “th” and so on. (She acted as if she heard sibilants so well that no one could believe she was hearing impaired.9
- Had superb lip reading ability.
- Would respond to a very faint and deliberate hiss and could be called from the opposite end of her home if someone simply hissed sharply.
- Refused standard hearing aids, and seemed to do much better without them than with them.10
Dr. Berlin continues, “These errors in classification stem from the almost normal sensitivity to environmental sounds that contain broad-band transients or sibilant-like hisses. Their extraordinary hearing outside the standard range also allows them to develop unusually fine speech in both the sibilant articulation areas and even speech timing, provided they are not forced to wear powerful binaural aids, which occlude their ears and mask their good high-frequency hearing. When they take pure-tone audiograms, they appear to have substantial losses though the speech range (300 to 3000 Hz), which is grossly incompatible with their communication abilities.”11
Dr. Berlin then cautions, “These people are difficult to diagnose unless one is vigilant for their salient characteristics: unusually good speech and sensitivity to environmental sounds in the presence of poor speech perception (without visual cues) and severe pure-tone hearing losses in the presence of unusually good speech-detection thresholds. Their audiograms suggest they are hearing impaired or deaf, while their behaviors suggest that they have good hearing sensitivity and speech production, but poor speech perception. Many of these people reject standard hearing aids and often function well without them.”12
A simple way to test for the presence of a reverse-slope hearing loss is to use the Ling 5 sound test (ah, oo, ee, ss, sh). The tester should stand behind the person being tested and using his own natural voice, pronounce “ah, oo, ee, s, sh” with even intonation, asking the person to raise a hand each time anything is heard.
When a person has a fairly-severe reverse-slope loss, you will notice that they hear the “s” and “sh” sounds at much softer sound levels than the “ah, oo, and ee” sounds.13
Here are 8 characteristics that those of us with severe reverse-slope losses generally have. If we exhibit most of these characteristics, we very likely have a severe reverse-slope loss. These characteristics include:
- Hearing loss of 70 to 110 dB at 1,000 Hz.
- Better than expected Speech Recognition Threshold (SRT) scores for this degree of hearing loss, i.e. excellent speech detection.
- Do not like wearing conventional hearing aids.
- Remarkably precise articulation (i.e. great speech) without any amplification.14
- Poor pitch control when singing.15 (e.g. I can’t tell when my voice is pitched to a given note when I am singing. In fact, I don’t even have a clue in which “key” I am singing!)
- Higher-pitched voices when not wearing hearing aids, yet virtually perfect articulation, especially of fricative sounds such as “f” “v” “s” and “z”.
- Excellent language expression and comprehension.
- Readily hear selected higher-frequency environmental sounds.16
High-Frequency Testing Is the Answer
Most of the above problems with misdiagnoses could be instantly eliminated if audiometers were designed with our hearing losses in mind—i.e. were sensitive down to at least -30 dB and were calibrated to test hearing up to 20,000 Hz, and if audiologists would consistently test people to the highest frequency, and softest sound, they can hear.
Unfortunately, modern audiometers generally only test to 8,000 Hz, rather than up to 20,000 Hz. Back in the mid 1960s, I was tested with an old audiometer (old in those days too) that was calibrated to cover the frequencies well above 8,000 Hz.
At 1,000 Hz I couldn’t hear anything until the volume was set quite high (probably about 7 or 8 out of a range of 0 to 9). However at the highest frequency tested (16,000 or 20,000 Hz), I could hear all the way down to 0 and it was still loud to me. I bet the tester that I could take the earphones off and hold them at arm’s length, and since the volume was as low as it would go, if she would turn the power switch off and on, I could tell her when it was on or off—and I did. This illustrates the incredible sensitivity of our high-frequency hearing. It’s about time the audiometers we need are readily available to test our hearing!
Amplification for Reverse-Slope (or Low Frequency) Losses
People with reverse-slope hearing losses have completely different amplification needs than people with the much more common ski-slope losses. Thus, effectively fitting hearing aids, cochlear implants and assistive devices to people with reverse-slope losses requires a somewhat different approach than is usually taken.
Hearing Aids and Reverse-Slope Losses
People with reverse-slope losses often ask, “Which is the best hearing aid for my kind of hearing loss?” In the past there were no “best” hearing aids. In fact, there weren’t even any “good” hearing aids for us. No wonder Terry lamented, “Is there any kind of hearing aid for my kind of hearing loss? It seems everything out there is for high frequency loss.”
Hearing aid manufacturers have not concerned themselves with the unique needs of people with reverse-slope hearing losses. They just make hearing aids for the most common kind of hearing loss (the ski-slope loss). From their point of view, there are not enough of us for them to have the financial motive to develop a hearing aid to fit us.
Think about it. Since reverse-slope losses like mine only occur in 1 person in 12,000 hard of hearing people, assuming that all of us with reasonably-severe reverse-slope losses bought such hearing aids, the manufacturers would be able to sell a total of maybe 3,000 or so in North America! Not much of an incentive, is it?
Some people with reverse-slope losses have wondered why hearing aids such as the AVR ImpaCt, a high to low frequency-transposing hearing aid designed specifically for those with severe ski-slope losses, couldn’t be reverse designed to transpose the low frequencies to higher ones.
For example, Patti wrote, “It seems that they should be able to develop a hearing aid that could take low frequencies and compress them into the high frequencies so that we could hear more.”
You may be surprised to learn that some years ago (back in the 1980s), Drs. Berlin, Halperin and Killon did exactly that. They designed some experimental hearing aids that transposed the lower frequencies to the higher frequencies that those of us with reverse-slope losses can hear well. Dr. Halperin ultimately made 50 prototypes of these special translating aids.17
However, not everyone who tried one of these aids liked them because all sounds were higher pitched, making people sound more like Mickey Mouse than human. They took a bit of getting used to.
When one lady began wearing this special translating hearing aid, she wrote, “It sounded very strange and for the first hour or so I fooled around with the translator and direct aid controls. Voices sounded like jabberwocky because they were so different. I opened a door and let it slam. I expected the slam would be harsh but it wasn’t—a surprise! My cousin spent the evening with us and I tried the aid while conversing with him. He has a low voice and I often needed to strain to follow his conversation. Well, the hearing aid unquestionably made his voice clearer and easier to follow. I found myself relaxing while listening to him, and I was able to understand him despite the fact that he has a mustache. Later in the evening I listened to the sounds of a lively New Orleans jazz band; it was loud but not glaring.”18
Fortunately, with new digital hearing aid technology, having frequency-transposing hearing aids is much less of a concern. This is largely because of two innovations. The first is that new digital hearing aids have multiple channels in them (typically between 7 and 16). (Note: channels are basically just a way of dividing up the audio frequency spectrum so that each channel can be programmed independently from each other.) Thus you can have your hearing aids set to exactly match your hearing loss—frequency by frequency. Therefore, theoretically, you can properly program digital hearing aids to match any reverse-slope loss.
The second innovation is the development of wide-band hearing aids. Typical hearing aids cover the frequencies up to 6,000 or 8,000 Hz. The new wide-band hearing aids work up to 16,000 Hz where those of us with reverse-slope losses typically have much of our hearing.
Because we hear relatively well between 4 kHz and 16kHz, we need hearing aids that don’t amplify these high frequencies much—but, at the same time, allow these sounds to come through without obstruction, and yet amplify lower-frequency sounds.19 It is critical that our hearing aids don’t block or mask the high-frequency sounds that are so important to us. We use the very high-frequency sounds to understand speech, and to recognize environmental and warning sounds.
My current hearing aids are the very first wide-band (16,000 Hz) hearing aids America Hears produced. They work well for me. In contrast, Rusty tried the Widex Inteo (Widex IN-19) and is having excellent results with them.
Fitting Hearing Aids to People with Reverse-Slope Losses
Since reverse-slope hearing losses are quite rare, few audiologists have much experience programming hearing aids to meet our needs. The truth is, fitting hearing aids to people with reverse-slope hearing losses is not as straightforward as it first seems. There is no cut and dried method that works for everyone.
Many audiologists rely on the manufacturer’s fitting software. However, programming our hearing aids according to the manufacturer’s theoretical programming protocols seldom (if ever) works for us, especially if we have the more severe reverse-slope hearing losses. Audiologists that do this end up with unhappy patients like Terry, Judith and Dolores.
Terry wrote, “I have a couple of Siemens in-the-ear, programmable aids that have been mostly useless because I can’t get them programmed right.”
Judith explained, “The audiologist I now rely on says I have a “reverse-slope loss”. The hearing aid I now have is less than satisfactory. The audiologists I have been going to have told me it is a very difficult loss to correct, and each would rather the other assist me. It is not fun to spend $2,650.00 for unsatisfactory equipment!”
Dolores was totally upset with her fitting experience. She related, “My audiologist adjusted my hearing aids according to the manufacturer’s fitting protocol. When I walked out, the door squeaked loudly and my footsteps rang in my ears. I started the engine and the roar overpowered the radio. My nerves were shot by then, and I began to cry.”
It is obvious that the programming software just doesn’t make proper provision for people like us. In fact, the audiologist my wife goes to told me she wouldn’t be able to program digital aids to fit me because of the software limitations.
The reason for this is that we perceive sounds somewhat differently than normal—especially if we have had reverse-slope hearing losses from birth. Doreen explained, “My audiologist said reverse-slope losses are harder to fit because each person’s perception of normal sound is so different.” Audiologist Brad Ingrao, Au.D. definitely agrees. He wrote, “The real trick, in my experience, is in unraveling the pattern of loudness and pitch perception in a reverse-curve loss. I haven’t ever found a reliable pattern, so ended up taking each one individually.”
Since this is the case, audiologists need to follow Brad’s example—really listen to us, then specifically set the volume by frequency to what we like—and largely forget about the theoretical fitting curves and suchlike if they want to successfully fit reverse-slope hearing losses. As Doreen discovered, “The computer program tells the audiologist what settings to use based on my audiogram. They set my aid as specified by the computer and it was awful. I ended up with my aids set almost opposite to what the computer said it should be.”
Nancy explained, “Fitting a reverse slope loss is somewhat counter intuitive. My audiologist had to turn off the ‘learning’ programming in my new hearing aids. It would try to adapt my hearing aids to my environment. Unfortunately, the algorithms were developed with the usual high-frequency hearing loss in mind. As a result, it completely messes things up for those of us with reverse slope losses.”
Audiologists can’t follow their fitting algorithms when fitting me either. I don’t understand speech well when my audiologist sets my hearing aids the way they are theoretically supposed to be set. To me it sounds like a person talking with several whole plums in his mouth (if that is possible)! It is bassy, boomy and largely unintelligible.
I need my hearing aids programmed according to how my brain perceives speech, not slavishly following my audiogram. This means programming my hearing aids so everyone sounds more like Mickey Mouse. Since my brain has never heard low-frequency sounds well, it thinks that sounding like Mickey Mouse is normal, so that is where I understand speech the best.
I think the reason my hearing is like it is results from two key factors. First, I had a severe reverse-slope hearing loss from birth. As a result, my brain didn’t know that speech contained a lot of lower-frequency sounds. Second, I did not get hearing aids until well after my brain had “wired” itself to think that normal speech was largely devoid of low-frequency sounds. (Your brain finishes wiring itself around age 6 or 7.)
As Evan Hillman, another person born with a reverse-slope hearing loss explains, “By being born with RSHL, my brain decided over 50 years ago that some portions of spoken sound are useless to me. Amplifying and presenting this portion of speech to my brain does not help because I have not developed neural pathways to utilize it. At best, the sounds will be useless. At worst, the sounds will increase my level of confusion.”
Speech contains a lot of redundancies. “Given the choice, our brains will do as little work as possible. Therefore, as we first learn language, our brains decide what minimum portions of a given sound it will use to decode the sound into meaningful speech. Because of our RSHL, those of us born with it use a different sampling of sounds to decode speech.”
In my case, I didn’t wear a hearing aid until I was 15 years old (although I had tried one for a few months when I was 8). By that time, I understood speech only when the high-frequency sounds were predominant. Thus, I needed my hearing aids set to the way my brain understood speech—not to the way the audiogram indicated my hearing aids should be programmed.
In contrast, my younger daughter, who has a similar reverse-slope loss to mine, began wearing two hearing aids when she was 3 or 4—while the auditory circuits in her brain were still plastic. Thus her hearing aids allowed her brain to wire itself more normally.
Evan explains, “Logically, it makes sense to only amplify the sounds our brains are able to use most effectively. Most audiologists don’t realize that the sounds most useful to a person with reverse-slope hearing loss are different than those of a person with normal hearing, especially a normal hearing loss acquired as an adult. In my opinion this is one of the core reasons we are always fighting with our hearing aid providers.”
Apart from getting fitted with hearing aids at a very young age while the brain is still plastic, there are two other secrets to successfully fitting hearing aids to people with reverse-slope losses. These both address the same problem, but they do it in two different ways.
The problem is that we need to hear the very high-frequency sounds we rely on to understand speech. Unfortunately, the higher frequencies our brains learn to use is prone to a lot of interference from environmental noise (crackling leaves, shuffling papers, running water, etc.) that don’t bother those with normal hearing, but really affect us. As a result it takes us much more effort to filter these sounds out so we can understand speech than it does for those with normal hearing. Therefore, we need our hearing aids fitted to how our brains understand speech the best. If this is not done, we end up as frustrated as Dolores.
She explained, “I’ve tried hearing aids twice before and have once again begun trying another. I’m having an awful time with it. I don’t understand what people are saying, and even with the hearing aid it’s not helping—everything is muffled and the phone is a nightmare.”
Dolores is experiencing problems because her hearing aids and/or ear molds are blocking the very high-frequency sounds she needs for understanding speech. Without these high-frequency sounds, to us speech sounds all muffled.
Therefore, when you fit hearing aids to people with reverse-slope losses, you need to be aware of the serious deleterious effects that occluding our ear canals has on us. Whenever, or if ever, our ear canals must be occluded by hearing aids or ear molds, you need to provide some other way for us to hear very high-frequency sounds.
There are two ways to do this. The first way is to use non-occluding ear molds. These can be either open-fitted ear molds, or ear molds with vents of sufficient size to allow us to hear the high-frequency sounds we need.
The second way, especially if open-fitted ear molds or vented ear molds will cause feedback, is to fit us with special wide-band hearing aids that amplify sounds up to 16 kHz or higher, rather than topping out at 6 or 8 kHz as regular hearing aids do.
The secret here is to program the aids to “pass through” these very high-frequency sounds, even though we have normal hearing in this range, because the ear molds are blocking us from otherwise hearing them.
If this is not done, we will complain that you are giving us too much low-frequency amplification, and not enough high-frequency amplification.
Traditional hearing aids both mask and occlude the high-frequency portion of the hearing spectrum. This forces us to use the less effective, low-frequency hearing we have at our disposal,20 rather than our good high-frequency hearing on which we generally rely, and that frustrates us.
This was Missy’s problem. She wrote, “The trouble I have experienced is when they give me what I need to boost my lows, it overpowers my highs.”
Liz has a similar problem. She writes, “Part of my problem is that my aids have been programmed with too much lows and not enough highs.”
Liz further states, “My audiologist doesn’t want to fix that because she feels that I need the lows, and that my highs are essentially normal, but I told her I’m not getting the consonants to help me differentiate between words.”
Liz is absolutely right. Her audiologist is programming in too much low-frequency amplification.
This stems from two different fitting philosophies. The better NAL fitting philosophy is to equalize, rather than normalize loudness relationships across speech frequencies. If all the speech frequencies are amplified so that they are heard equally loud, speech intelligibility is maximized.21
However, when other fitting methods try to preserve this normal relationship of loudness among the speech frequencies, they tend to prescribe too much gain for the low frequencies.22
Therefore, the key is to amplify less at frequencies where there is severe to profound hearing losses, which in the case of reverse-slope losses means the low frequencies, and amplify more at the frequencies of better hearing.23 This is because the frequency regions of poorest hearing will contribute the least towards speech intelligibility.24 In fact, this is the principle of effective audibility.
As Ted Venema, Ph.D. explains, “Effective audibility refers to how much information can be extracted from speech sounds once they are audible. As hearing loss increases, for people with severe or greater hearing loss, a small sensation level might give some amount of information, while a high sensation level will not necessarily add much more information for understanding speech. Thus for those with profound hearing loss, audibility might be accompanied with virtually no added effective audibility.25
This seems to be the problem with the fitting philosophy in Missy’s and Liz’ cases.
In fact, for properly fitting reverse-slope losses, the NAL-NL1 fitting protocol does not target any gain below 500 Hz, and reduced gain at 500 Hz itself, because these frequencies will not contribute to effective audibility.26
Thus for effectively fitting reverse-slope losses, we need reduced low-frequency amplification so it does not overpower the high-frequency and very high-frequency amplification on which we so much depend.
Finally, never forget about the effects of recruitment (where certain sounds are perceived as much too loud). Recruitment can be a real problem for those of us with reverse-slope losses. At some frequencies, my recruitment is quite severe. Unfortunately, these are the very frequencies I need to understand speech. Thus by setting the compression levels for comfort, it means I no longer have as good as discrimination as otherwise—but at least I can stand the recruiting sounds, so this is a mixed blessing.
To be effective, at least in my experience, compression needs to be programmed into our hearing aids frequency by frequency. Unfortunately, few audiologists program compression this way. Francis Kuk, Ph.D. in his study of people with reverse-slope hearing loss concluded:
- A digital multi-channel nonlinear hearing aid has more features than a linear hearing aid to match the gain requirement of people who have a low-frequency hearing loss.
- Use of wide dynamic range compression (WDRC) with a low compression threshold (CT) and high level compression may be more effective (than linear or WDRC with high CT) in preserving audibility and maintaining comfort across listening environments.
- People with a reverse-slope audiogram do prefer amplification in the low frequencies. However, their gain preference, compared to the recommendations of some proprietary fitting targets, may vary depending on input levels.
- A broad bandwidth, including amplification in the normal or near-normal frequency region, is desirable. However, the specific amount needs individual customization.27
One word of caution in relation to Dr. Kuk’s conclusions: from what I can determine, the people he studied generally fell into the Class 1 reverse-slope category. Therefore, his conclusions need to be modified to include such things as wide band hearing aids and allowing pass-through very high frequency sounds, as I have explained above, in order to apply more particularly to people with Class 2 and Class 3 reverse slope losses.
Oticon has a 15-minute podcast that explains the principles of effectively fitting hearing aids to people with reverse slope hearing losses. In it, Oticon’s Don Schum explains much of what I have explained above with graphs and charts/audiograms. You would do well to watch/listen to it now.
Note: just because a person has a reverse-slope hearing loss doesn’t guarantee that a hearing aid will help him. For example, people with Auditory Neuropathy/Auditory Dys-synchrony (AN/AD) often have reverse-slope hearing losses, yet such people generally do not benefit from wearing hearing aids (with some notable exceptions, although they often benefit from cochlear implants). Therefore, it is important to test middle ear muscle reflexes, otoacoustic emissions and auditory brainstem response to ensure a proper diagnosis of the problem.28
The salient features of people with AN/AD include:
- Otoacoustic emissions are, or at one time were, present.
- Auditory Brainstem Response (ABR) is absent or grossly abnormal.
- Middle ear reflexes are absent.29
People that have AN/AD fit the above conditions, yet they may have a very pronounced reverse-slope audiogram (Fig. 7). According to Dr. Berlin, “In AN/AD the audiogram is virtually meaningless, so before you try to treat a reverse-slope loss, you have to rule out AN/AD because no hearing aid easily helps it.”30
Cochlear Implants and Reverse-Slope Losses
Since not many hard of hearing people have reverse-slope losses, it follows that not many have received cochlear implants (CI) either. Thus, for those with extreme reverse-slope losses, there is little history of how well cochlear implants will perform.
This has led to concern on the part of people with reverse slope losses that they won’t get good results with a cochlear implant. For example, Lorene wrote, “I am scared that if the CI didn’t work, I would not be able to use what is left of my residual hearing in my right ear.”
Part of this concern stems from the fact that ski-slope losses and reverse-slope losses have residual hearing at opposite ends of the cochlea. The cochlea is shaped like a snail, and consists of 2½ turns. High frequency hearing occurs at the base and low frequency hearing at the tip (apex).
With the normal ski-slope loss you basically have no high-frequency hearing left, so when the doctor inserts the cochlear implant electrodes into the base of the cochlea where they would normally destroy any residual high-frequency hearing, there is none there left to lose. Also, since the electrodes don’t quite reach the tip where the low frequencies reside, some residual low-frequency hearing may remain.
Furthermore, with a reverse-slope loss, the residual (high-frequency) hearing is at the base of the cochlea where it is destroyed when the electrodes are inserted. Thus, people with reverse-slope losses have more to risk in that sense if the cochlear implant should fail to work well for them.
However, if you wait until your hearing is so poor and garbled that you can’t understand much anyway, you really don’t have much to lose, so why worry about keeping any residual hearing?
As noted in the previous section, in Dr. Berlin’s experience, people with AN/AD often do well with a cochlear implant, in spite of having reverse-slope losses. For example, the person whose audiogram is shown in Fig. 7 “benefited remarkably from a cochlear implant” according to Dr. Berlin.
Programming a cochlear implant for a person with a long-standing extreme reverse-slope hearing loss likely will be quite a challenge since cochlear implant fitting protocols are set up for those that have the typical ski-slope loss. When people with a ski-slope loss get a CI, they typically tell how all voices then sound high-pitched and Mickey-Mousey. This is because they haven’t heard high-frequency sounds for years. Now, all of a sudden, the CI gives them those sounds.
In contrast, a person with a reverse-slope loss, when turned on, not having heard low-frequency sounds for years or a lifetime, will likely find the low-frequency sounds overpowering. In fact, this is exactly the case with one who reported that voices now sounded very low-pitched and growly and were mostly incomprehensible.
I can well believe this for when my hearing aids are programmed for “normal” I also feel like I am being drowned in a sea of loud, low-frequency incomprehensible noise. A partial solution seems to be in turning off a number of the low frequency electrodes. Only time will tell what the real solution will ultimately prove to be.
Assistive Devices and Reverse-Slope Losses
If you have a more severe reverse-slope loss, you will soon find that a number of the wonderful assistive devices to help hard of hearing people hear better are not so wonderful after all. This is because they have been engineered in such a way that we cannot hear and understand speech well when using them.
This is especially true when we try to find an amplified phone we can hear on. For example, Karen wrote: “We were at a seminar where a Clarity (new name for the old Ameriphone/Walker company) representative was heavily pitching their “Clarity Power” telephones as hot new items that are to replace the old Ameriphone line. When asked from the audience “why was there no tone control with Clarity Power” the engineer said that tone controls are obsolete, and that it is much better to have the tone embedded in the volume control so that as the volume increases, so does the frequency emphasis. He was pretty strong in his having “engineer expertise” so no one challenged him.”
Karen then asked: “Am I missing something in my understanding of what the combined tone/volume control does? How would someone get the right amplification in their frequency range? I’m pretty sure I’m right, but I’m not an engineer.”
This is a classic example of engineers doing shoddy research into the needs of hard of hearing people.
If he had said that the Clarity products were designed only for hard of hearing people with ski-slope losses, I would have agreed with him that having an integrated volume and tone control might be a smart idea.
However, such a design is stupid for people with flat losses and cookie-bite losses, and is totally asinine for those of us with severe reverse-slope losses. If he had ears like mine, he would never have made such a ridiculous statement.
This is much the same kind of thinking that went into the design of a wonderful phone for hard of hearing people—the Williams Sound Teletalker™ phone. To their credit, the designers included both a volume and a tone (they call it an enhance) control.
Unfortunately, they bought into the above misconception about what all hard of hearing people need. Although this phone is billed as having 55 dB of gain (which would be wonderful for my hearing loss), instead of putting all the power into the volume control, they assumed that hard of hearing people would never need more than 25 dB of overall gain, so they put 25 dB gain into the volume control, and then put the other 30 dB of gain into their tone (enhance) control.
Since I need much more than 25 dB of basic gain, I need to crank the tone control way up to get the required volume, but, by the time I have enough volume, all that extra high-frequency gain so distorts people’s voices that I can’t understand them.
Thus I have a wonderful phone designed specifically for hard of hearing people, yet I can’t use it. I’ve suggested to Williams Sound that they put all the gain on the volume control, but so far, they have ignored my suggestion.
As an effective workaround for both the TeleTalker and the Clarity phone I now use, I have added the Ameriphone HA-40 in-line amplifier. This neat little gizmo has separate volume and tone controls. Thus, I can add in the extra volume I need without distorting the higher frequencies.
To be sure, there are a number of other assistive devices that have straight volume or have both volume and tone controls that work pretty well for us. For example, the Williams PockeTalker personal amplifier has both volume and tone controls and works great for me.
Since our perception of speech is so different from other hearing losses, it is imperative that we try out any assistive devices before we buy them to be sure they will work for us (or be allowed to return them if they prove unsatisfactory).
Join the Reverse-Slope On-line Support Group
If you (or a family member) have a reverse-slope loss and would like to join an information and support email list for people (and parents of children) with reverse-slope hearing losses (RSHL), click on Subscribe to RSHL Support Group and then press “Send” to send a blank email to Yahoo Groups. Reply to the confirmation email you’ll receive to activate your subscription. You can unsubscribe at any time.)
Berlin, Charles I., et. al. 1978. Superior Ultra-Audiometric Hearing: A New Type of Hearing Loss Which Correlates Highly with Unusually Good Speech in the Profoundly Deaf. ORL.
Berlin, Charles I. 1980. Ultra-Audiometric Hearing in the Hearing Impaired and the Use of Upward-Shifting Translating Hearing Aids. Kresge Hearing Research Laboratory of the South. Louisiana State University Medical Center. New Orleans, Louisiana.
Berlin, Charles I. 1985. Unusual Forms of Residual High-Frequency Hearing. In: Seminars in Hearing—Volume 6, Number 4. Kresge Research Laboratory, New Orleans, Louisiana.
Berlin, Charles I., et. al. 2002. Chapter 8, The Physiological Bases of Audiological Management. In: Hair Cell Micromechanics and Otoacoustic Emissions. Singular.
Berlin, Charles I., et. al. 2003. Auditory Neuropathy/Dyssynchrony, Its Diagnosis and Management. Pediatr. Clin. N. Am. 50 (2003) pp. 331-340.
Kuk, Francis, et. al. 2003. Changing with the Times: Managing Low-Frequency Hearing Loss. Hearing Review, November 2003. http://devdomino.widexpro.com/images/researchArticles/DAR61.pdf.
Venema, Theodore. 2001. The NAL-NL1 Fitting Method. Audiology Online. http://www.audiologyonline.com/articles/article_detail.asp?article_id=253.
1 Berlin, 1985. p. 389.
2 Berlin, 1980. p. 50.
3 Berlin, 1980. p. 48.
4 Berlin, 1978. p. 111.
5 Berlin, 1985. p. 392.
6 Berlin, 1985. p. 393.
7 Berlin, 1980. p. 53.
8 Berlin, 1978. p. 112.
9 Berlin, 1985. p. 391.
10 Berlin, 1985. p. 389.
11 Berlin, 1980. pp. 53-54.
12 Berlin, 1980. p. 54.
13 Berlin, 1985. pp. 393-394.
14 Berlin, 1980. p. 50.
15 Berlin, 1978. pp. 111-112.
16 Berlin, 1980. pp. 44-45.
17 Berlin, 1985. p. 392.
18 Berlin, 1980. p. 50.
19 Berlin, 1980. p. 46.
20 Berlin, 1980. p. 49.
21 Venema, 2001. p. 2.
22 Venema, 2001. p. 3.
23 Venema, 2001. p. 4.
24 Venema, 2001. p. 7.
25 Venema, 2001. p. 4.
26 Venema, 2001. p. 5.
27 Kuk, 2003. p. 6.
28 Berlin, 2002. p. 139.
29 Berlin, 2003. p. 333.
30 Berlin, 2006. Personal communication.