Hearing range
Introduction
The hearing range is the range of frequencies that can be heard by humans or other animals, though it can vary from one species to another. The human hearing 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.
Human Hearing Range
Humans are most sensitive to frequencies between 2,000 and 5,000 Hz. Certain high-frequency sounds can be perceived even at levels up to 120 dB at frequencies as high as 10,000 Hz, but are more commonly perceived in the lower part of this range. The upper limit of the human hearing range decreases significantly with age. A healthy young person can hear frequencies from approximately 20 to 20,000 Hz. The highest frequency that a normal middle-aged adult can hear is only 12–14 kilohertz. Also, humans are most sensitive to frequencies between 2,000 and 5,000 Hz.
Animal Hearing Range
Different species have different hearing ranges. For example, dogs can perceive vibrations up to 60,000 Hz, and cats up to 79,000 Hz. Some species of dolphins and bats can hear frequencies up to 100,000 Hz. Elephants can hear sounds at 14–16 Hz, while some whales can hear infrasonic sounds as low as 7 Hz.
Factors Affecting Hearing Range
Several factors can affect the hearing range, including age, prolonged exposure to loud noise, genetics, and environmental factors. Age-related hearing loss, or presbycusis, begins in early adulthood and progresses throughout life. Long-term exposure to loud noise can damage the hair cells in the cochlea, causing noise-induced hearing loss. Certain genetic syndromes can also affect the hearing range. Environmental factors such as altitude or pressure can also affect the perception of sound.
Measurement of Hearing Range
Hearing range is typically measured by a series of tests known as audiometry which measures a subject's hearing levels with respect to the collective 'normal' hearing levels. The threshold of hearing is plotted relative to a reference level.
Implications of Hearing Range
The implications of different hearing ranges are numerous. In the animal kingdom, it can affect an animal's ability to detect prey or predators, communicate with others, and navigate their environment. For humans, it can affect our ability to communicate, enjoy music, and interact with our environment. There are also implications for the design of audio equipment, such as speakers and headphones, as well as public warning systems and other audio-based technologies.