The question of whether sharks make noise is complex, as the answer depends entirely on the definition of “noise.” Sharks are often perceived as silent hunters, and while they do not possess the biological apparatus for true vocalization like marine mammals, they are far from mute. The distinction is between intentional, modulated sounds for communication and the incidental or mechanical noises produced as a byproduct of their movement and behavior. Sharks rely heavily on sound for survival, but their relationship with sound is primarily centered on reception rather than production.
Why Sharks Cannot Vocalize
Sharks belong to a class of fish called Chondrichthyes, characterized by a skeleton made entirely of cartilage. This fundamental anatomy explains why they cannot produce the complex sounds that whales or dolphins do. Sharks lack a larynx, or voice box, which is the structure containing vocal cords necessary for creating modulated, intentional sounds.
The anatomical limitations extend further into the internal organs that many other fish species use to generate sound. Most bony fish, for instance, vibrate a gas-filled organ called the swim bladder to produce drumming or grunting noises, which can be used for communication. Sharks, however, do not possess a swim bladder; this organ would interfere with their need for constant movement to maintain buoyancy. Sound production in many fish relies on either this resonating bladder or stridulation, which is the rubbing of bony parts together. Since sharks lack these specialized features, they do not possess the means to vocalize for the purpose of communicating with their own species.
Mechanical Sounds Made by Sharks
While sharks cannot vocalize, they do produce sounds that are mechanical in nature, occurring as a direct result of their physical actions in the water. These noises are incidental and often loud, serving as a byproduct of feeding or threat displays. A sharkâs rapid movement at the surface can lead to powerful tail slaps and loud breaches that create significant acoustic energy in the water.
A recent study recorded small bottom-dwelling species called rig sharks (Mustelus lenticulatus) producing sharp, high-frequency clicking sounds when handled. This discovery challenged the long-held belief that sharks are silent, revealing a potentially active form of noise production. The clicks are theorized to be produced by the forceful snapping of their dense, pavement-like teeth, a defensive action rather than a communicative signal. These abrupt clicks can exceed 155 decibels, a volume comparable to a shotgun blast, and may serve as a startling distraction for a potential predator. Significantly, the high frequency of these recorded clicks falls outside the rig shark’s best hearing range, suggesting the noise is not intended for communication with other sharks.
How Sharks Use Auditory Senses for Survival
Although sharks are not built to produce complex sounds, their ability to receive sound is highly refined and a primary tool for survival. Sharks possess an inner ear structure that is extremely sensitive to disturbances in the water, and they combine this with a unique sensory system called the lateral line. The inner ear detects particle motion, which is the actual vibration of water molecules, rather than the sound pressure that mammals perceive.
Sharks are particularly adept at detecting low-frequency sounds and vibrations, specifically those under 1,000 Hertz. They are most attracted to irregular, pulsed sounds in the range of 25 to 100 Hertz, which is precisely the acoustic signature of a wounded or struggling fish. Sound travels faster and farther underwater than it does in air, allowing sharks to detect these distress signals from distances as great as a mile away, making hearing their most effective long-range sense.
The lateral line system, which runs along the sides of the body and over the head, functions alongside the inner ear to form the acoustico-lateralis system. This network of fluid-filled canals senses low-frequency pressure changes and water flow in the immediate vicinity. This allows the shark to detect the precise movements of nearby prey, even in dark or murky water. The interplay between the inner ear, which detects distant sounds, and the lateral line, which senses close-range vibrations, allows the shark to efficiently track and localize a potential meal.