Frequent(cy) Hearing

Frequent(cy) Hearing

   The visiting by my mother brought another unexpected surprise, a view of the changing world of hearing.  Her own hearing had worsened, but it was only now that she agreed to the possibility of needing hearing aids...and the testing for hearing has changed (at least to my viewpoint) dramatically.

   Beyond the frequency tests one usually hears (and if you think you're immune and can hear perfectly fine, it might be worth taking the quick test on Brain Games, the series available online or at your library;  in a room filled with people from ages 8 to 70, ever higher frequencies began to be emitted...by the third range of frequency, I could hear nothing, which it turns out is typical for my age group; at the end, only the 8 year-olds could hear the higher test frequencies, although even they will lose that frequency range by the time they reach their teens), hearing tests now conduct speech frequencies, the computer constantly adjusting the hearing aids to the results of your hearing (no clicking or speech on your part is required for this portion of the test...the computer is simply measuring your response to the sounds of language).  The speech is a jumble of small pieces of 6 languages, English, German, French and a few others that were difficult to pick out (perhaps Yiddish?).  As I listened in over the speakers (since I wasn't the one actually taking the test), my brain struggled to pick out each language, trying to make some sense of what was being said and in what language. A snippet of English would appear, followed by a half-second of something in German, blended with a half-second of something else.  It was fascinating, as if hearing a entirely new language and trying desperately to make sense of it.

    Part of this is due to our brains which has to unscamble it all; our ears simply take in the frequencies, much as our eyes merely take in the light.  It is up to our brains to make sense of it all, and that can be where the problems occur.  The jumble of words I heard was likely the most recent word recognition test described by the Merck Manual as one which, "tests the ability to discriminate among the various speech sounds or phonemes.  It is determined by presenting 50 phonetically balanced one-syllable words at an intensity of 35 to 40 dB above the patient's SRT (speech reception threshold).  The word list contains phonemes in the same relative frequency found in conversational English."   Another test given relied on the conduction of frequencies not through the ear but rather through the bone (it is suspected that this may be how whales hear such low frequencies in the water).

   We, as humans, have a rather limited hearing range, much as our eyesight is limited to such a small spectrum (NOVA's excellent film, Earth From Space, said that if the light spectrum was spread out from New York to Los Angeles, the light spectrum we see would be equal to the size of a dime...a dime!).  Cats can hear way beyond our abilities (even more so than dogs).  And it remains a mystery how elephants can carry low frequencies not through the air but through the ground (as you're likely aware, stories abound of animals sensing an earthquake or tsunami hours ahead of it actually happening).  But perhaps our limitations extend not only to our ears, but also to our recording and monitoring instruments...who knows what other "sounds" or frequencies may be out there?

    Hearing a grand concert or watching something or hiking in the woods are all sounds we seem to take for granted, even as we enjoy them.  But, perhaps like a simple conversation, there is an entire world out there we're missing, sometimes because we've simply lost the ability...but sometimes because we've simply stopped listening.