I, too, have been watching this subject -- with dread...

When I was young, and up to my 40's, I could hear the ultrasonic burglar alarm
transducers in department stores (they are left on 24 hours). In fact, I hated
going into those stores precisely because of that -- the piercing, knife-like
assault was just too much for me. Other people would say, "Huh? Whaddayoumean?
What sound?"

Nevertheless, at the same time, I had hearing damage from sonic trauma in my
right ear. So the hearing damage we hear about all the time might not always
affect the higher frequencies. My hearing damage was caused by the US Army.
Unfortunately, before I was drafted in 1960, I had several years of marksmanship
training, and I was quite good. So during basic training I was employed to coach
the guys who were having troubles - usually terrible flinching. That coaching
meant you placed your face in front of the face of the trainee, so you were
looking right into his eyes and at his trigger finger. That placed your right
ear about two inches from the breech of an M1 rifle. And if you've ever fired
one of those, you know the breech action is nearly as noisy as the actual
explosion, not to mention the ejected cartridges whanging off your helmet. I had
hundreds of rounds go off into that ear. (It was a court martial offense to wear
any kind of hearing protection back then. I believe the exact opposite is true
today.) I ended up with a severe "notch" in my right ear hearing measured at
about 7KHZ, yet that same ear could hear stuff above 20KHZ. I never put a phone
to that ear because speech intelligibility is really affected.

Today, at 58, I feel fortunate that I ~can't~ hear ultrasonic alarms any more,
but I can still hear Golden-crowned Kinglets and Grasshopper Sparrows. I dread
the day I assume will come when I can no longer hear those birds.

So not all sonic trauma kills the high end, but I'm sure some trauma does. One
might find that with a hearing aid filling in the "intelligence" areas of
hearing, the perception of the higher frequencies might be better. Who knows? If
the hearing aid amplifies the upper register, maybe it would help people with
progressive loss of the higher frequencies - at least until their loss becomes
just too great. I don't think the high end just switches off - it slowly
deteriorates. OTOH, hearing aid vendors have not had the best reputation over
the years for product claims. The old Latin phrase, "Caveat try it out before
you buy it emptor" applies in this case, I'm sure.

Jerry


E-mail from: Jerry Blinn, 26-Apr-1996