Hearing

Hearing, or auditory perception, is the ability to perceive sounds through an organ, such as an ear, by detecting vibrations as periodic changes in the pressure of a surrounding medium.

[5] The middle ear consists of a small air-filled chamber that is located medial to the eardrum.

Within this chamber are the three smallest bones in the body, known collectively as the ossicles which include the malleus, incus, and stapes (also known as the hammer, anvil, and stirrup, respectively).

The round window, another flexible membrane, allows for the smooth displacement of the inner ear fluid caused by the entering sound waves.

Inside the organ of Corti is the basilar membrane, a structure that vibrates when waves from the middle ear propagate through the cochlear fluid – endolymph.

Basilar membrane motion causes depolarization of the hair cells, specialized auditory receptors located within the organ of Corti.

[7] The sound information from the cochlea travels via the auditory nerve to the cochlear nucleus in the brainstem.

The inferior colliculus in turn projects to the medial geniculate nucleus, a part of the thalamus where sound information is relayed to the primary auditory cortex in the temporal lobe.

Such tests include auditory brainstem evoked potentials (ABR), otoacoustic emissions (OAE) and electrocochleography (ECochG).

The various means used to prevent hearing loss generally focus on reducing the levels of noise to which people are exposed.

In species that use sound as a primary means of communication, hearing is typically most acute for the range of pitches produced in calls and speech.

Snakes sense infrasound through their jaws, and baleen whales, giraffes, dolphins and elephants use it for communication.

Some fish have the ability to hear more sensitively due to a well-developed, bony connection between the ear and their swim bladder.

Georg Von Békésy in 1929 identifying sound source directions suggested humans can resolve timing differences of 10μs or less.

[19] Even though they do not have ears, invertebrates have developed other structures and systems to decode vibrations traveling through the air, or “sound”.

Charles Henry Turner was the first scientist to formally show this phenomenon through rigorously controlled experiments in ants.

Video showing how sounds make their way from the source to the brain
Schematic diagram of the human ear [ clarification needed ]
The middle ear uses three tiny bones, the malleus, the incus, and the stapes, to convey vibrations from the eardrum to the inner ear.
The inner ear is a small but very complex organ.
The lateral lemnisci (red) connects lower brainstem auditory nuclei to the inferior colliculus in the midbrain.
A cat can hear high-frequency sounds up to two octaves higher than a human.