Did you hear that? Nah, didn’t think so. But hey, I’ll bet your cat did. A cat’s ear is a marvelous feat of engineering. This, in large part, is because of that elegantly arched ear tip, called a pinna. Humans have pinnae too, but in my opinion, not nearly as attractive. Ours certainly don’t have the mobility that a cat’s ear has. Our pinnae lie flat and immobile against the head and are highly sculpted.
A cat’s ear can swivel – independently – a full 180 degrees. And cat ears are smooth, except for a narrow pouch located at the ear’s outer base.
So what is that thing on my cat’s ear, and what’s it for, anyway? Its anatomical name is the cutaneous margin pouch. More commonly it’s known as a Henry’s Pocket.
Its function, though, is debatable – and here’s why:
The study of how we perceive sound is called psychoacoustics. As the name suggests, it’s a combination of the hard and soft sciences: acoustics and psychology. In other words, there are some things about hearing that are measurable in concrete ways, and some things that aren’t. This is because research must rely on the input of the person or animal being studied to evaluate how a sound is perceived.
We can ask a human subject to describe a sound we play (including where the person heard it, how long it lasted, how loud it was, and so on). But because we haven’t yet figured out how to speak cat with any degree of accuracy, we’re limited to our observation of their reactions.
A surprising number of opinions exist on cats and their hearing. Do an web search and you’ll find tons of articles, many with contradictory information and some with some pretty wild claims (including “Your cat can hear the electric currents in your house”).
It takes a bit longer to track down actual, published studies in such places as the Journal of Physiology, but they’re out there, and here’s what they tell us:
The range of high and low frequencies cats can hear is much greater than that of humans or dogs. In fact, it’s only slightly less than that of the porpoise. The exact hearing range varies from subject to subject, just as it does in humans. It also depends on the volume of the sound.
Loudness is measured in decibels. A normal conversation is around 55 dB to 65 dB. A dishwasher or washing machine is 70 dB to 75 dB. Most humans describe the most ‘comfortable’ sounds as at or below 60 dB. Hearing damage begins at 85 dB.
Studies using a 70dB signal strength show a cat can hear a frequency as low as 45 Hertz. The upper threshold has been measured as high as 85 kiloHertz. One study indicated that “four and a half year old cats were distinctly less sensitive than yearlings.” (Guess it sucks getting older whether you’re human or feline.)
Sound localization is the ability to identify a sound’s point of origin, specifically its direction and distance. Cats’ hearing is so keen that according to one study, they are “the best sound localizers of any terrestrial mammal.”
Draw an invisible line horizontally directly in front of them and they can pinpoint a sound to within 5 degrees. That means they’re able to differentiate sounds 3 inches apart at 3 feet, or a bit more than 2 feet apart at a distance of 25 feet.
How do you rate? Try this: ask someone to stand ten feet away from you while holding a ball point pen in each hand (this needs to be the “clicker” type – the kind that makes a noise). Ask the person to hold the pens about 10 inches apart, then close your eyes and see whether you can distinguish which hand “clicked.”
Interestingly, a cat’s accuracy drops significantly when the sound is elevated. Accuracy at elevation degrades to 15 degrees, which means birds have three times the advantage over prey that scurries around on the ground. This diminishes once the cat tilts his head up because the horizontal axis is now also tilted up (see diagram below).
So, back to that thing on my cat’s ear
To understand how the pouch at the base of your cat’s ear might help with his hearing, we’ll look at ours again. There’s a reason the human ear is so contoured. Those hills and valleys function as tuners, amplifying some frequencies and diminishing others. Though not yet demonstrated to the satisfaction of all researchers, the theory is that a cat’s cutaneous margin pouch functions in much the same way, focusing and directing certain sounds into the ear canal.
Oh yeah, about that rumor that cats can hear the electrical current in your home? File that one under Ways to Annoy a Physicist. After a 5-minute rant, my husband (yeah, he’s a physicist) told me that if someone tries to sell you that tale … don’t buy it.
The short explanation: In order for electrical current to cause a sound, it has to create a displacement in the air – you know, a sound wave. Electricity can do that – after all, that’s why lightning is followed by thunder – but it happens only at high energy levels.
Ever heard the buzzing of a transformer high up on a utility pole? That’s not the electricity you’re hearing, that’s the electrical current interfacing with the insulator as the current passes by, causing a physical disturbance in the air, which is to say, a sound wave.
Bottom line: If your cat hears electrical currents in your home – it’s time to evacuate.
Read more cool cat science stuff by Lisa Richman:
About Lisa Richman: Writer, director, pilot, foodie, cat person. When she’s not on set, this director of film and video can usually be found taking photos of cats (and food) with her trusty Nikon, or cruising aloft at 3,000 feet. She’s cat mom to an opinionated Tonkinese, a hearing-impaired Siamese, and a feline fashionista. She’s also the owner of a recently launched food blog, and the Cat Writer’s 2014 Entertainment Blog, A Tonk’s Tail.