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Re: Hearing aids

Author: sdr
Date: 2007-05-04 02:28

Some interesting issues about hearing aids and hearing rehabilitation are coming up in this thread. I am provoked to write some more:

Some "high end" hearing aids now offer multiple filter pre-sets -- something like setting the different radio channels on your car radio. Each setting (done for you by your dispensing audiologist, or by using factory default settings) is supposed to optimize your hearing in different acoustical environments. For example, speech in quiet, speech in noise, music, etc. Some "demanding listeners" and technophiles love this and find it to be a great help. Other people just want an on-off switch and a volume control. The situation is somewhat analogous to your microwave oven -- it has settings to roast a turkey, bake a pie, make popcorn, and defrost a TV dinner, but you probably just use it on "High" for 30 sec to reheat your cup of coffee. So, do you want to pay for all those other features?

When all is said and done, hearing aids are just amplifiers -- they make sounds louder. However, not all cases of hearing loss are due solely to loss of loudness. When we test hearing, we measure threshold (the softest sound you can hear at each test frequency, going up by octaves from 250Hz-8kHz) AND we measure hearing clarity (a.k.a. Word Recognition Score or Discrimination). Discrim is measured by having a voice (preferably from a high quality CD recording) read single syllable words (consonant envelope with a vowel in the middle; "You will say: CAT" "You will say: MIT" "You will say: BUT") and the test-taker repeats them. The audiologist scores the percentage of words repeated correctly. Normal persons score above 90% when the words are delivered at a loudness of 40dB above your threshold. Threshold and Discrim (loudness and clarity) are analogous to the volume and the tuner on a radio. Many people who lose hearing lose BOTH loudness and clarity. If you lose significant clarity, turning up the volume will not solve your problem. It's like turning up the volume on a radio station with bad reception -- you hear MORE, not BETTER. If you have a hearing loss of both loudness and clarity, hearing aids are still helpful to correct the deficiency of loudness, but they will not restore "normal" sound reception because of the degraded clarity. Unless the dispensing audiologists explains this and patients "recalibrate" their expectations, the patients are often very disappointed that their $6K investment ($3K/ear) sounds so crummy.

If you have a hearing test showing that you are a candidate for amplification, there is no benefit in postponing acquisition of hearing aids. Use of aids does not accelerate hearing loss nor foster dependency on the aids. However, once you use the aids and realize how much you've been missing, you will probably want to use them more often. Hearing aids are not bolted to your head. You use them when you want and take them off when you want. Once you have them, you have an option that was absent before you got 'em.

-sdr
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Steven D. Rauch, MD
Assoc. Prof., Otolaryngology
Harvard Medical School
Mass. Eye & Ear Infirmary

Tel: 617-573-3644
Fax: 617-573-3939
Email: steven_rauch@meei.harvard.edu
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