by Neil Bauman, Ph.D.
A man asked:
Is it possible for hearing aids to be programmed to deal with “recruitment”, the loud “bursty” elements of sound?
This seems to be quite a common problem for those of us with more severe hearing losses. Few audiologists seem to take the time to properly test for recruitment, and then specifically adjust our aids so they don’t cause recruitment.
The proper way to test for recruitment is to check the uncomfortable loudness levels (UCL) where sounds go from being too loud to hurting for each test frequency.
Typically, audiologists just do a “broadband” check of the UCL, rather than frequency by frequency. In fact, only one time in my life has an audiologist ever done a proper frequency by frequency recruitment check, and that was because I specifically asked her to do it.
After testing for the UCL frequency by frequency, your audiologist then needs to set the compression on your hearing aids for each frequency to limit the maximum sound level for those frequencies such that they always remain below your recruitment level.
This sounds simple in theory—but may be harder to do in practice depending on the number of compression bands your hearing aids have. Because of the placement of my recruitment along the frequency spectrum, and since by hearing aids only have four compression bands, my audiologist has to “detune” half of my channels in order to fix the recruitment problem. The result is that my comprehension goes down significantly. This is not good.
Thus I have two choices: either fix most recruitment problems, but don’t understand as much of what I hear, or understand more of what I hear, but yank my hearing aids out of my ears when sounds start recruiting. Either way, I don’t hear as much as I should. The next time I get hearing aids, I’m going to look for hearing aids where the compression can be set for each frequency—not just by broader bands.
Totally eliminating recruitment isn’t easy. There is a fine line you have to walk when adjusting the hearing aids to get the best of both worlds at the same time. It won’t be perfect, but with patience, your audiologist should be able to get pretty close.
My husband has severe recruitment. He is interested in “compression” hearing aids. Are these a specific type of hearing aid or are they regular hearing aids are tuned to specific frequencies? Any information is greatly appreciated.
Hi Kim:
I daresay that all modern digital hearing aids have compression built into them. So basically it is just a matter of the dispenser adjusting the compression by frequency to accommodate his recruitment. Their first step is to determine at what level for each test frequency that recruitment occurs. Then they need to set the compression a bit lower than that figure for EACH frequency. Too often, they don’t set the compression by frequency and this is not very helpful when you you have severe recruitment.
Cordially,
Neil
I am apparently a rare bird. Overnight, 6 months ago, I acquired unilateral Class 2 RSHL with severe recruitment. I am looking into getting a hearing aid. Many folks with RSHL recommend vented domes, but due to the recruitment my audiologist wants me to try unvented -to better filter out the recruitment frequencies. Do you have any advice about the domes and/or programming?
Hi Terry:
Yes, I think you are a rara avis alright. A sudden severe reverse slope hearing loss is not something I think I’ve ever run across. What do you think caused your hearing loss?
Normally, audiologists want unvented domes/ear molds so the louder low frequency sounds they amplify don’t cause feedback. But this is predicated on wrong thinking. First, unvented domes/ear molds don’t let you hear the high frequencies in that you hear normally, but are not amplified in your hearing aids. Thus, unvented domes leave you partially deaf in the high frequencies.
Second, you don’t want much amplification in the low frequencies at all. You want the main amplification on the slope up. Thus, without the strong low frequency amplification, you don’t need unvented domes.
You can learn the principles of properly fitting hearing aids for people with reverse slope losses near the end of my comprehensive article on the subject at http://hearinglosshelp.com/blog/the-bizarre-world-of-extreme-reverse-slope-hearing-loss/.
Your audiologist should read this section as they typically don’t have a clue how to properly program hearing aids for RSHL. They may say they do, but they don’t. This is because programming for RSHL is NOT intuitive, but counter-intuitive, and many refuse to program them that way because they think it is wrong. So you need to find an audiologist that will work with you to program your hearing aids to what works for you, not to what they think is the proper way to program them.
Cordially,
Neil
Thanks, Neil. My hearing loss is considered ideopathic. I had no exposure to loud noise and no symptoms prior to the morning I woke up with it. Can you explain more about testing MCL & UCL? I never understood why the audiologist wanted me to indicate the level I “could stand listening to for 30 mins.” If I “tolerated” something that irritating for 30 minutes, I’d be totally exhausted by it for hours afterward. I think she listed that as an MCL of 55dB, with an UCL of 70dB.
Hi Terry:
Your most comfortable listening level is exactly what it says—that is the level you would comfortably listen to speech all day not just 30 minutes. Your MCL of 55 dB sounds about right. On the other hand you’re uncomfortable listening level is basically where sound becomes too loud, not for 30 minutes, but even for 10 seconds. A normal UCL is around 110 dB. It’s the level of sound just before it becomes painfully loud. Your UCL is only 70 dB. I don’t think that’s true. I think you misunderstood what your audiologist meant and so you don’t have a true reading. If you truly had a UCL of only 70 dB you would have a severe case of hyperacusis.
Cordially,
Neil
Thanks again! Very helpful to know what mcl stands for. I think my audiologist was trying to figure out a level that I could “tolerate” even if uncomfortable, so I’d get some speech recognition out of my bad ear. But as far as I’m concerned, I’d rather get rid of the distortion -even if it meant nearly all my speech recognition had to come through the other ear. Fingers crossed for a collaborative programming session a week from this Friday. (BTW I do SNHL with severe recruitment. Below about 1800Hz, ordinary sounds are way too loud for me: I keep tv & radio at the lowest volume setting, keep asking people to speak more softly, and have to wear earplugs in stores with Muzak.)
This is very interesting. I have severe to profound hearing loss with recruitment. My audiologist has not yet found a comfortable solution. In the meantime, do the very loud sounds produced at frequencies affected by recruitment cause further damage to my hearing?
Hi Hilary:
Recruitment (and loudness hyperacusis) are where you PERCEIVE a sound as being very loud–often so loud that it hurts–but the real sound is not all that loud–and it is real sounds that cause damage, not perceived high sound levels.
So the answer to your question is “no”, but the sound hurting is very real to you.
Cordially,
Neil