Final answer:
The missing words are 'stiff' and 'short', indicating that high-frequency sounds stimulate the basilar membrane's parts that are closer to the oval window because stiff and short objects resonate better at higher frequencies. The basilar membrane's movement varies according to the frequency of sound, supporting the place theory of pitch perception.
Step-by-step explanation:
The question asks us to insert the missing words: "High-frequency sounds mostly stimulate the parts of the basilar membrane that are closer to the oval window. The reason for that is that stiff and Select objects tend to resonate at higher frequencies." The correct missing words for 'Select' are 'short', so the complete sentence should read: "High-frequency sounds mostly stimulate the parts of the basilar membrane that are closer to the oval window. The reason for that is that stiff and short objects tend to resonate at higher frequencies."
The basilar membrane plays a crucial role in the process of hearing. It partitions the cochlea into the scala tympani and the scala vestibule and moves in response to the sound-induced pressure waves triggered by the oval window's vibration. High-frequency sounds primarily affect the basilar membrane's base near the oval window, while the apex gets activated by lower frequencies. This phenomenon agrees with the place theory of pitch perception, which suggests that specific regions of the basilar membrane vibrate by the frequency of the incoming sound waves.