Noise

Noise is random or unwanted sound. Unwanted signals, such as static that interferes with radio transmission, are also referred to as noise. The sound we hear is caused by vibrations of air molecules. A tuning fork produces an almost pure tone, with only one frequency, or rate of vibration (see Tone). Musical instruments produce harmonic sound. Such sound contains many frequencies, called overtones, that are harmonically related (see Harmonics). Random sound has many overtones that are not harmonically related. Mechanical devices produce such sound.

Unwanted sound can be caused by any kind of sound--tones, harmonic sound, or random sound. Sound is unwanted if it is annoying or distracting, or if it damages the hearing mechanism.

Contributor: Thomas A. Griffy, Ph.D., Prof. of Physics, Univ. of Texas, Austin.

See also Acoustics; Decibel; Muffler; Sound.

Noise

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