Increasing the amplitude of a sound most directly increases which mechanical response?

Increasing the amplitude of a sound most directly increases which mechanical response?

• A. Displacement of the basilar membrane
• B. Size of the tympanic membrane
• C. Frequency of basilar membrane vibration
• D. Number of outer hair cells activated

Answer: (A)

When you increase the amplitude of a sound, the amount of energy in the wave increases, and the most direct mechanical consequence inside the cochlea is a larger displacement of the basilar membrane. The basilar membrane responds to the pressure-driven traveling wave by moving more back and forth as the input level rises, so its motion scales with sound amplitude. Frequency, on the other hand, is determined by the stimulus frequency and the place along the membrane that is driven, not by how loud the sound is. Activation of outer hair cells depends on this motion to produce neural signals, so it’s a downstream effect of the initial basilar membrane displacement rather than the immediate mechanical response to amplitude.

When you increase the amplitude of a sound, the amount of energy in the wave increases, and the most direct mechanical consequence inside the cochlea is a larger displacement of the basilar membrane. The basilar membrane responds to the pressure-driven traveling wave by moving more back and forth as the input level rises, so its motion scales with sound amplitude. Frequency, on the other hand, is determined by the stimulus frequency and the place along the membrane that is driven, not by how loud the sound is. Activation of outer hair cells depends on this motion to produce neural signals, so it’s a downstream effect of the initial basilar membrane displacement rather than the immediate mechanical response to amplitude.