Final answer:
The tympanic membrane vibrates most effectively when sound frequencies align with its mechanical properties and the basilar membrane vibrates in resonance, converting sound waves into electrical signals for the brain to interpret.
Step-by-step explanation:
The tympanic membrane vibrates most effectively when pressure waves from sound match its mechanical properties, such as its ability to flex at different frequencies. When sound waves enter the ear, they cause the tympanic membrane to vibrate. These vibrations are then transmitted through the middle ear bones and into the cochlea of the inner ear. Figure 14.12 illustrates how these vibrations reach the cochlea and create pressure waves in the cochlear fluid.
In the cochlea, the cochlear duct has a membrane that bends at a point of maximum vibration for a given frequency. This causes the hair cells in the basilar membrane to vibrate. As a sound wave causes these hair cells to move back and forth, they brush against the overlying tectorial membrane, which is also vibrating due to the pressure waves. The interaction between the hair cells and the tectorial membrane converts the mechanical energy of the sound waves into electrical signals that the brain can interpret.
The basilar membrane has unique mechanical properties that vary along its length, thus allowing it to vibrate at different locations based on the frequency of incoming sound. The tectorial membrane accordingly vibrates at different positions, which contributes to our ability to detect the pitch of sound and, with additional cerebral processing, to determine the direction from which the sound is coming.
In summary, the tympanic membrane operates most effectively when the frequencies of incoming sound waves are conducive to the natural vibration patterns of the ear's anatomical structures, particularly the basilar and tectorial membranes.