How does the basilar membrane help the ear distinguish high pitches from low pitches?

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

As sound vibrations travel through the cochlea, they create traveling waves that reach their maximum amplitude at specific locations on the basilar membrane based on their frequency. This occurs because the membrane is not uniform: it increases in width and mass while decreasing in stiffness from its base (near the oval window) to its apex.12

• High-frequency sounds: These cause the stiffer, narrower basal end of the membrane to vibrate most vigorously.12
• Low-frequency sounds: These cause the more flexible, wider apical end to vibrate.12

When a specific region vibrates, it stimulates the hair cells in the organ of Corti at that location. The brain identifies the pitch by recognizing which group of nerve fibers is activated by these vibrations.1