Sound: Encyclopedia II - Sound - Perception of sound

Sound - Perception of sound

The frequency range of sound audible to humans is approximately between 20 and 20,000 Hz. This range varies by individual and generally shrinks with age. It is also an uneven curve - sounds near 3,500 Hz are often perceived as louder than a sound with the same amplitude at a much lower or higher frequency. Above and below this range are ultrasound and infrasound, respectively. The amplitude range of sound for humans has a lower limit of 0dBSPL, called the threshold of hearing. Sound is technically at its upper limit at 194.09 dB. Above this level it should be called a shock wave. Sounds begin to do damage to ears at 85 dBSPL (with prolonged exposure - eg 8 hrs per day) and sounds above approximately 130 dBSPL (called the threshold of pain) cause pain. Again, this range varies by individual and changes with age.

The perception of sound is the sense of hearing. In humans and many animals this is accomplished by the ears, but loud sounds and low frequency sounds can be perceived by other parts of the body through the sense of touch. Sounds are used in several ways, most notably for communication through speech or, for example, music. Sound perception can also be used for acquiring information about the surrounding environment in properties such as spatial characteristics and presence of other animals or objects. For example, bats use one sort of echolocation, ships and submarines use sonar, and humans can determine spatial information by the way in which they perceive sounds.

Adapted from the Wikipedia article "Perception of sound", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki