The membrane that vibrates differently depending on sound frequency is called?

• A. Basilar membrane
• B. Round window
• C. Tectorial membrane
• D. Vestibular membrane

Answer: (A)

Frequency-to-place mapping along the cochlea explains why this membrane vibrates differently for different frequencies. The basilar membrane changes along its length: it’s stiffer and narrower at the base and more flexible toward the apex. When sound travels into the inner ear, it creates a traveling wave on this membrane, and the peak of that wave occurs at a location that depends on the frequency. High-frequency sounds peak near the base, while low-frequency sounds peak nearer the apex. This spatial pattern is what allows the auditory system to separate different tones. The other membranes have important roles (for example, the round window moves to balance pressure, the tectorial membrane interacts with hair cells to help transduce motion, and Reissner’s (vestibular) membrane separates scalae) but they do not produce the frequency-specific vibration patterns that the basilar membrane does.