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.