It's true that it's not just a sense of smell that's much stronger in cats than humans. A cat's sense of hearing is also remarkably superior to that of humans.
While humans and cats have a similar range of hearing on the lower end of the scale, cats can hear much higher-pitched sounds. According to LSU's article on Deafness and Hearing Range, a cat's hearing range (in Hz) is 45-64,000, compared to 64-23,000 in humans. This means that cats can hear sounds we can't hear on both ends of the spectrum, but particularly on the higher end. Cats are not only above the range of a human, but they are also beyond the range of dogs, by at least one octave.
A Common Reaction From Cats
Cats' ears are uniquely designed to draw sound into the ear canal, which enables them to hear an array of distant sounds—like a mouse rustling in the bush 30 feet away. By the same token, their ears are more sensitive to the higher amplitude of the sound. It is common knowledge that humans' hearing can be compromised by repeated exposure to loud music. It's also possible that cats are more susceptible to potential deafness from the same cause.
Incidentally, an army experiment with cats backs up this theory. According to the Auditory Hazard Assessment Algorithm for Humans (AHAAH), studies have indicated that there are several auditory hazards that can occur from intense sounds that enter cats' ears. The study focused on cats who were anesthetized (to eliminate middle ear muscle activity) and then exposed to various places where impulses were produced at different peak pressures using a rifle gun.
Symptoms of Hearing Loss
There are several symptoms of hearing loss, from experiencing unresponsiveness to loud noises, to seeing them walking unbalanced. If your cat looks disoriented, has reddened ear canals, or other symptoms, it's important to take him or her to the vet as soon as possible. Additional observations can include black or yellow discharge from the ears, or a change in behavior, like not realizing you're in the room until he or she is touched.
Protecting Your Cat's Ears
Your cat's reaction to the loud music and/or excessive noise is an instinctive act of self-protection. Heed the signals your cat is sending and try to tone down the volume when he or she is in the room.
Similar to humans, cats can develop hearing problems over time due to disease, infection, trauma, damage, and simple old age. You can protect your pet's hearing with gadgets like Mutt Muffs or simple earplugs made out of foam or cotton balls.