Final answer:
Humans have heightened sensitivity to sounds within the middle-frequency range of hearing, essential for conversation and music. Hearing tests cover frequencies from 250 to 8000 Hz, with hearing loss affecting the clarity and appreciation of these sounds.
Step-by-step explanation:
Human hearing is especially sensitive to sounds with frequencies that fall in the middle portion of the audible range. This sensitivity relates to the range of frequencies that most conversational sounds fall within, which is quite effectively illustrated by the frequency and intensity region shaded in the provided figure. Human hearing can encompass an impressive frequency range from 20 Hz to 20 kHz, including the range that is most important for understanding conversation and appreciating music. Hearing tests are commonly performed from 250 to 8000 Hz, which covers the range crucial for these aspects of daily life. The threshold of hearing in these tests is measured in dB relative to a normal threshold, with typical hearing registering as 0 dB across all frequencies. Losses in hearing, such as a 40-phon hearing loss, can still allow for an understanding of the conversation, albeit much quieter. A more significant 60-phon loss can lead to difficulties, especially with higher frequencies, affecting the clarity of speech and music appreciation.