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5. Pitch “ImPerfect”

HearResponsibly Yours, Musings from a Seasoned Hearing Scientist

Human hearing is naturally tuned to sounds that have supported our ancestors to survive, keep us in the gene pool, and exchange spoken messages. The growl of four-legged predators and the hiss of poisonous snakes were fortunately in our zone of hearing – or we would likely not have survived past the Ice Age. Although compared to many other animals our audible range (bandwidth) is somewhat limited, yet we have not only survived but prevailed to ‘top of the food chain’ status. Sounds that thump and boom in the deepest registers, form the bottom of our best hearing range. Follow the tones of a piano fully to the left and you’re almost at the bottom of that audibility. A grand piano can vibrate around 27 times a second (Hz). Just a few cycles lower and you’ve reached the infrasonic range where you are more likely to ‘feel’ the vibrations than hear them.

One of the properties of our ‘acoustic anatomy’ is the length of the ear canal happens to be about one inch.  Like any other ‘tube’ it has a natural best pitch which tends to favor hearing many soft ‘high pitch’ consonants -like “SS” occur in speech.  That natural ear canal resonance conceivably contributed to the development of our spoken vocabulary since it make it easier to hear and distinguish between say, ‘Sixty-Five’ versus ‘Fifty-Five’ or ‘Fake’ versus ‘Sake.’  But the same natural amplification of that pitch region, around 2700 to 3200 Hz, also made boosted the sound of many modern tools and repetitive noises to excessively loud and damaging with levels.  It’s the pitch region where noise-related damage tends to first show up on audiograms.  Higher frequencies (pitches) routinely show damage before lower tones in sensori-neural hearing loss and the earliest signs often reflect the natural boost around 3000 Hz. (Less common, and more treatable, middle ear problems tend to have a different pitch pattern). 

That common high pitch damage creates a muffling effect that impacts “Clarity.”  Those soft, higher pitched consonant like “S, Sh, F, TH, P” are important carriers of meaning causing many ‘hearable’ words to become ambiguous, especially in poor or noisy listening conditions. So, the typical frustrating experience is to hear plenty – but with ‘imperfect pitch.’ Those affected will report ‘sure, they can hear’ – but people mumble, or there’s so much more noise than the ‘old days.’   So when a manager mistook an order in the office for Fifty-Five Thousand Foozles and shipped Sixty-Nine Thousand Swoozles it was a costly, and possibly career-ending error of imperfect pitch.

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