Hearing range describes the frequency range that can be heard by humans or other animals, though it can also refer to the range of levels. The human range is commonly given as 20 to 20,000 Hz, although there is considerable variation between individuals, especially at high frequencies, and a gradual loss of sensitivity to higher frequencies with age is considered normal. Sensitivity also varies with frequency, as shown by equal-loudness contours. Routine investigation for hearing loss usually involves an audiogram which shows threshold levels relative to a normal.
Several animal species can hear frequencies well beyond the human hearing range. Some dolphins and bats, for example, can hear frequencies over 100 kHz. Elephants can hear sounds at 16 Hz–12 kHz, while some whales can hear infrasonic sounds as low as 7 Hz.
- ^ Multiple sources:
- Fay, R.R. (1988). Hearing in Vertebrates: A Psychophysics Databook. Winnetka, IL: Hill-Fay Associates. ISBN 9780961855901. LCCN 88091030.
- D Warfield. 1973. The study of hearing in animals. In: W Gay, ed., Methods of Animal Experimentation, IV. Academic Press, London, pp 43–143.
- ^ Multiple sources:
- Fay and AN Popper, eds. 1994. Comparative Hearing: Mammals. Springer Handbook of Auditory Research Series. Springer-Verlag, NY.
- CD West. 1985. The relationship of the spiral turns of the cochela and the length of the basilar membrane to the range of audible frequencies in ground dwelling mammals. Journal of the Acoustical Society of America 77:1091-1101.
- EA Lipman and JR Grassi. 1942. Comparative auditory sensitivity of man and dog. Amer J Psychol 55:84-89.
- HE Heffner. 1983. Hearing in large and small dogs: Absolute thresholds and size of the tympanic membrane. Behav Neurosci 97:310-318.