hear

Hear is the sense by which sound is perceived. It refers to both the physiological process and the act of perceiving auditory stimuli. In everyday use, to hear is to notice sounds, while listening implies intentional attention and interpretation of what is heard.

An auditory pathway begins with the outer ear collecting sound waves and guiding them to the middle ear, where the eardrum and three small bones (the ossicles) amplify vibrations. The inner ear contains the cochlea, where mechanical vibrations are converted into electrical signals by hair cells. These signals travel via the auditory nerve to the brain, and the auditory cortex processes information about pitch, timing, and loudness to identify sounds, their sources, and their meaning.

Hearing ranges and sensitivity vary by species and age. Humans typically hear from about 20 Hz to 20 kHz, with sensitivity measured in decibels (dB SPL). The average quiet threshold is near 0 dB at comfortable frequencies, but sensitivity can decline with age or prolonged exposure to loud noise. Hearing encompasses detection, localization, and interpretation of a wide array of sounds, including speech, music, and environmental cues.

Hearing loss denotes reduced ability to hear sounds and can be conductive, sensorineural, or mixed. Causes include aging, noise exposure, disease, and genetics. Management options include hearing aids, cochlear implants, and other assistive devices, along with protective measures to prevent further damage.

Auditory testing, such as pure-tone audiometry and speech audiometry, assesses hearing thresholds and comprehension. Newborn hearing screening helps identify early deficits. Across the animal kingdom, hearing ranges vary widely, with some species detecting ultrasound or infrasonic frequencies far beyond the human range.