Fish can detect sound, though not in the same way humans do. They use a combination of inner ear structures called otoliths and a sensory system called the lateral line. The inner ear picks up sound waves transmitted through water, while the lateral line, a series of fluid-filled canals along the body, detects pressure changes and low-frequency vibrations. Together, these systems give fish a surprisingly detailed awareness of their acoustic environment.

Species with a swim bladder connected to the inner ear, such as goldfish and certain catfish, hear a broader frequency range than those without this connection. These fish can detect sounds roughly from 20 Hz to several thousand Hz, overlapping with much of the human hearing range.

Fish can learn to associate specific sounds with events. Many aquarium keepers notice their fish swim to the front of the tank at feeding time in response to footsteps, the sound of a food container opening, or a gentle tap on the lid. This is a conditioned response rather than true recognition, but it demonstrates that fish process and remember auditory cues.

Whether fish recognize individual owners is debated, but studies suggest some species can distinguish between familiar and unfamiliar human faces and may associate certain people with feeding. This is likely more visual than auditory, though the combination of seeing and hearing a familiar person approaching reinforces the response.

Loud noises and sudden vibrations stress fish significantly. Placing a tank away from speakers, slamming doors, and heavy foot traffic helps keep them calm. Tapping on the glass should be avoided as it creates intense pressure waves inside the water that are startling and stressful.