by Neil Bauman, Ph.D.
A man asked:
When an audiologist says you have a ‘mixed’ hearing loss, what exactly does he mean?
Hearing loss basically comes in 4 “flavors”.
First, there are conductive losses. Conductive losses comprise about 10% of all hearing losses. They are typically mechanical hearing losses in the outer and middle ear and often involve the lack of free movement of the 3 tiny bones in the middle ear—the hammer (malleus), anvil (incus) and stirrup (stapes).
Second, there are sensorineural hearing losses. Sensorineural (pronounced SENS-sore-ree-NOO-rawl) hearing losses are the most common kind of hearing losses, comprising about 90% of all hearing losses. These hearing losses have to do with the auditory sensing nerves in the inner ear and auditory nerves (hence the name sensori—sensing, and neural—nerves). In the past this was referred to as “nerve deafness”. However, this is really a misnomer as the hearing loss almost always occurs because of the death of the hair cells that connect to the very tips of the auditory nerves, not to the nerves themselves.
Third, is the rare central hearing loss. Central hearing losses occur when something is wrong in the auditory processing parts of the brain. Your ears can be working properly but you still can’t hear well because your brain can’t process these sound signals correctly.
Finally, and also rare, is a functional hearing loss. Functional hearing losses are psychological hearing losses that can occur after severe trauma, for example. Such people have been so traumatized that they block out all sounds so don’t hear them, although the entire auditory system is working properly.
Now that you know the kinds of hearing losses, it is easy to answer your question. A mixed loss is where you have 2 or more of these hearing losses occurring at the same time.
Typically, when audiologists refer to a mixed hearing loss, they are talking about your having both a sensorineural hearing loss and a conductive hearing loss at the same time.
They can tell this because there is an “air-bone gap” on your audiogram. Unlike its name suggests, there is no physical gap between two bones in your head letting air in. Rather, this is your audiologist’s shorthand way of saying that the results of your air conduction test (what you hear through your ear canals when wearing earphones) and your bone conduction test (what you hear through your skull when wearing a bone vibrator behind your ear) are not the same—the two lines do not overlay each other as would happen if you only had a sensorineural hearing loss. Instead, there is an gap or space between the “air” and “bone” conduction lines when plotted on your audiogram.