Final answer:
Audition exhibits both sustained and transient responses at frequencies up to about 4000 Hz after which higher frequencies are encoded mainly using place cues. The hearing is most sensitive in the range of 2000 to 5000 Hz, where the ear requires less intensity to perceive loudness.
Step-by-step explanation:
The student's question pertains to the auditory response at certain frequencies. Specifically, the question is asking at which frequency range does the human ear begin to exhibit both sustained and transient responses. The sustained response refers to the auditory system's ability to detect a constant sound over time, while the transient response indicates the detection of quick, short sounds or changes in sound quality.
Based on the references provided and additional information, the human ear displays a combination of rate of action potentials and place cues up to a frequency of about 4000 Hz, which contribute to our perception of pitch. Beyond 4000 Hz, higher frequency sounds are primarily encoded using place cues, as the rate of firing of auditory nerve fibers does not increase linearly with frequency above this point.
Furthermore, hearing tests, as shown in audiograms, are conducted over a range of 250 to 8000 Hz. Normal hearing registers as 0 dB across all frequencies on such tests, but hearing loss can often present as a dip near 4000 Hz, and in the case of presbycusis, it results in a loss that is more severe at the higher frequencies.
The region between approximately 2000 and 5000 Hz is where the ear is most sensitive, with dips in loudness curves reflecting this heightened sensitivity. For instance, sounds in this sensitive range require less intensity to be perceived as loud as those at other frequencies.