Does it seem like consonant sounds get harder to hear as the decades pass? In light of the delicate mechanism whereby we hear these sounds, it’s no wonder they become more difficult to discern. Mechanical stress wears away our sensory parts over time, and our brain is forced to fill in the blanks, sometimes erroneously.
Inside the fluid filled (1) cochlea in the inner ear (2), cilia protruding from hair cells bend in response to the vibrations of the tectorial membrane, sending sensory signals to the auditory nerve (2). The latter is “listening” to the aggregate of these cilia over time, which can tell us a lot.
According to Australia’s Macquarie University Department of Linguistics, the change in intensity of sound over time characterises various phonetic sounds (3). So vertebrates, who possess these ciliated sensors, are well equipped to differentiate such sounds.
I imagine that fish and frogs are more interested in discerning the sound of an approaching predator or a mating call than the phonetics of human speech, but these things have their analogues in phonics and can also be represented by changes in intensity of sound over time.
For humans, minuscule differences in sound pressure are used for speech. Vowel sounds have repeating peaks of intensity (3) and are relatively easy to hear. But the intensity of unvoiced consonant sounds is chaotic and non-repeating. (There are some wonderful illustrative graphs at Macquarie’s site!) No doubt your brain wants to hear the whole sound instead of anticipating a pattern that isn’t there. But it won’t if enough of those microscopic hair cells in your ear have died (2). They are not known to regenerate (2).
The sensory hair cells in the cochlea are very delicate instruments that are designed to sense tiny differences in pressure. They can easily be broken by loud sounds, so you must protect them. As you age, if you lose access to consonant sounds, the demise of cochlear hair cells is likely to be the cause of it.
Contact us if you have a concern related to hearing loss. Many problems can be prevented and remedied.