|How Well Cats Hear|
The cat relies on acute hearing as an essential part of its hunting arsenal. Cats don’t tend to chase prey for great distances. Instead, they listen for clues that prey is near, perhaps rustling beneath leaves, and then wait until the opportune moment to pounce. Their ears are fine tuned for this job.
The external ear (pinna) of the cat is large, erect, and cone-shaped. It acts to both catch and amplify sound waves. The cat’s ear amplifies sound waves two to three times for frequencies between 2000 and 6000 Hertz (Hz).
The cat can move its pinna around as much as 180 degrees, doing so by virtue of about 30 sets of muscles (you have only six sets). This enables it to lock into sound sources, but even the cat cannot move its ears fast enough to localize sounds.
Identifying the location of the source of a sound depends on processing the difference in both arrival time and the intensity of the sound as it arrives first at one ear, then the other. Because sound travels in waves, these differences are more apparent in smaller wave (higher frequency) sounds, and in fact are hard to detect if the sound waves are larger than the ears are spaced apart. For this reason, smaller animals have their ears far to the side of their head, and more importantly, are able to hear higher frequencies. Cats can localize high frequency sound sources that are only 3 inches apart from 3 feet away!
You and your cat share the same lower limit of about 20 Hz, but the difference in high frequency sound limits is great. Humans can hear frequencies up to 20000 Hz, dogs to about 45000 Hz, cats to 64000 Hz, and mice up to 95000 Hz. You are most sensitive to sounds of around 3000 Hz (most human voices are near that pitch), while your cat is most sensitive to sounds of around 8000 Hertz.
The pinna funnels the sound waves into the ear canal where the waves strike the ear drum. When the ear drum vibrates, it causes the three tiny ossicles (bones) to move, which in turn push on a membrane at one end of the cochlea. The cochlea is filled with fluid, so when the membrane is pushed it causes waves in the fluid. These waves flow over tiny hair-like cells that are sticking inward from the floor of the cochlea, causing some hair cells to move. Each hair cell sends a signal to the brain when it is moved, and depending on which cells are moved, your cat hears different pitched sounds. It is in these last steps that hereditary deafness usually disrupts.
Not Hearing Sound
Deafness is associated with white coat color in cats, but not all white cats are deaf. Deafness is most likely to appear in cats with the dominant white (W) gene. Cats can also be white due to the white spotting gene, but deafness is not associated with that gene.
According to one study, about 40 percent of white cats are deaf in both ears and 12 percent deaf in one ear. White cats with two white parents are more likely to be deaf in one or both ears. Cats with two blue eyes are more likely to be deaf than cats with one blue eye, and both are more likely to be deaf than cats with no blue eyes.
You can check your cat’s hearing by making startling sounds or hissing noises where your cat can’t see you (or other cats that may respond) or can’t feel any vibrations or wind currents. Deaf cats can learn to respond to vibrations and hand signals, but must be protected from outdoor dangers they cannot hear approaching.