Creature Comforts; I heard you, now shuddup
I got this urgent text message from my parents last weekend:
Spoiler alert: They did not explode. But, by the time my daughter and I got to their house, they were so on-edge, they were ready to call 911 in hopes that somebody in the fire department would know how to locate and disable the noise. I had visions of a well-meaning fireman chopping up the walls and ceiling of their kitchen with an ax, looking for some long-lost smoke detector, buried deep inside, somehow, after 20 odd years, giving off a low battery signal loud and strong. The sound had been going on for about 18 hours, and they had searched high and low for the source of the high-pitched, constant, electronic “eeeeeeeeeee” noise, without success.
To be fair, it was a very annoying noise. My daughter and I were able to zero in on its location after a quick canvass, and began our search for the source in an entirely different area of the kitchen than that which my parents had been concentrating their efforts. After so many hours of searching in vain themselves, they were initially convinced we were no closer to a solution than they had been, but were hopeful, nonetheless. It should come as no surprise that it was my daughter (with the help of her 16-year-old ears) who solved the mystery, and it took no more than 10 minutes, to my parents’ combined chagrin and profound relief.
Hearing is more than just detecting sounds. In fact, the anatomical and physiological intricacies of hearing are complex and crazy-cool. Heck, people with hearing problems (like my parents) may need to see multiple specialists: Audiologists, neurologists and otolaryngologists (ENT doctors). While not entirely essential for survival, hearing is a pretty nifty and convenient sense to have. Hearing helps us navigate spatially, avoid danger, find things we need like food, companions or lost children, and even stay on schedule (provided we don’t keep hitting “snooze.”) So when hearing malfunctions, it can cause some significant lifestyle changes, and may even be dangerous.
The next part gets science-y, but stick with me, you’ll thank me later. If you dislike science, we can’t be friends, and skip past the list. For the rest: Yay for science! Normal hearing involves the process of converting sound waves traveling through the air into neurological signals. AKA: Magic. Okay, not really. A much-simplified version of the process goes thusly:
1. The pinna (the outer ear flap) is shaped and positioned such that it captures and directs sound waves, funneling them into the auditory canal, where the sound is amplified by the shape and tissue composition of the ear canal. This and having a pair of ears on either side of our heads helps us focus on sounds, tell whether they are in front, behind or beside us, if they are near or far, and if they are moving or static.
2. The tympanic membrane (eardrum) is displaced by the sound waves, and as it vibrates, it moves the middle ear ossicles (super-tiny bones) which in turn vibrate against the oval window of the snail-shaped, fluid-filled organ called the cochlea in the inner ear.
3. The sound vibrations trigger the movement of tiny hairs within the cochlea (which specific hairs are triggered or how many hairs or how intensely will depend on the loudness of the sound and the frequency/pitch).
4. The movement of the hairs stimulates nerves, which send signals to the brain. Fun fact: Because each ear sends nerve signals to both sides of the brain, one-sided hearing loss cannot be the result of a brain lesion. Redundancy has its perks.
5. Once in the brain, the auditory signals trigger various responses that may be immediate (startle reflexes, rapid heart rate, increased respiratory rate, dilated pupils, “fight or flight.”) or more discerning (“What the heck was that?! The ice cream truck! Hungry! Chocolate, yum!)
6. As an interesting side note, we can hear higher frequencies underwater than we do through the air, as the sound waves stimulate a nerve response via bone conduction rather than the traditional path through the outer ear canal and eardrum. There are now bone-conduction headphones available that work on this principle.
So back to the noisome noise at my parents’ house. Turns out, it was a tiny, handheld, battery-operated personal alarm clock. Long forgotten, and apparently suddenly malfunctioning, it was squealing from inside a drawer. While I was inclined to hurl it dramatically from the window into the woods as if it were a grenade with the pin pulled, I did not. I neutered it, problem solved.
More to come about hearing, deafness and our pets in my next column.
— Daverio is a veterinarian at Williamsport West Veterinary Hospital. Her column is published every other Sunday in the Lifestyle section. She can be reached at firstname.lastname@example.org.