Sound reaches maximum amplitude depending on its frequency at:
**Core Concept**
The concept being tested here is the relationship between sound frequency and amplitude, particularly in the context of human hearing. The human ear is capable of detecting a range of sound frequencies, but the sensitivity and maximum amplitude of sound perception vary with frequency. This is due to the anatomical structure of the ear, specifically the basilar membrane, which plays a crucial role in sound processing.
**Why the Correct Answer is Right**
The correct answer is related to the concept of the "best frequency" or "resonance frequency" of the human ear. The basilar membrane, a critical component of the cochlea, is most sensitive to sound frequencies around 4000 Hz. This is because the basilar membrane has a specific frequency response curve, with maximum amplitude at around 4000 Hz. At this frequency, the basilar membrane is most responsive, allowing for the detection of even the smallest sound amplitudes. This is due to the mechanical properties of the basilar membrane, which is stiffer and more sensitive at higher frequencies.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the concept being tested. The maximum amplitude of sound perception is not related to the frequency response of the eardrum or middle ear.
**Option B:** This option is incorrect because the maximum amplitude of sound perception is not related to the frequency response of the auditory nerve. While the auditory nerve does play a critical role in sound processing, its frequency response is not directly related to the maximum amplitude of sound perception.
**Option C:** This option is incorrect because the maximum amplitude of sound perception is not related to the frequency response of the outer hair cells. While outer hair cells do play a critical role in sound processing, their frequency response is not directly related to the maximum amplitude of sound perception.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that the human ear is most sensitive to sound frequencies around 4000 Hz, which is why high-pitched sounds are often more easily detected than low-pitched sounds.
**Correct Answer:** C. 4000 Hz.