Hearing range usually describes the range of frequencies that can be heard by an animal or human, though it can also refer to the range of levels. In humans the audible range of frequencies is usually said to be 20 Hz (cycles per second) to 20 kHz (20,000 Hz), although there is considerable variation between individuals, especially at the high frequency end, where a gradual decline with age is considered normal. Sensitivity also varies a lot with frequency, as shown by equal-loudness contours, which are normally only measured for research purposes, or detailed investigation. Routine investigation for hearing loss usually involves an audiogram which shows threshold levels relative to a standardised norm.
Read more about Hearing Range: Determination of Hearing Thresholds, Land Mammals, Marine Mammals
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—Abraham Lincoln (1809–1865)
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