How does the basilar membrane separate high-pitched sounds from low-pitched sounds?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Meissner's corpuscle; mechanoreception — Mechanoreception In human skin, specialized nerve endings known as Meissner's corpuscles (or tactile corpuscles) are sensitive to touch. They are one of several different types of mechanoreceptors found in human skin.

The basilar membrane distinguishes pitch through a process known as the "place theory," which relies on the membrane's physical properties changing along its length.1

As the membrane extends from the base (near the oval window) to the apex (at the tip of the cochlea), it progressively increases in width and mass while decreasing in stiffness. Because of these structural variations, different regions of the membrane are tuned to vibrate most vigorously at specific frequencies:1

High-frequency sounds: These cause the stiffer basal end of the membrane to vibrate. The resulting traveling waves reach their peak amplitude quickly and travel a shorter distance along the membrane.1
Low-frequency sounds: These cause the more flexible apical end of the membrane to vibrate, with waves traveling further to reach their peak.1

When a specific region vibrates, it stimulates the hair cells in that area of the organ of Corti, which then send nerve impulses to the brain. The brain identifies the pitch by determining which specific group of nerve fibers was activated.1