What is noise?

Noise is a slight change in atmospheric pressure, which travels in waves. Noise can also occur through another medium, for instance through pulsations in water.

Noise can be perceived by people or animals with a hearing organ when the eardrum of the ear is made to vibrate and the hearing organ processes these vibrations into signals which are interpreted by the brain.

A noise source causes changes in atmospheric pressure which are transmitted through the air as sound waves. When such a sound wave reaches the eardrum, the latter begins to vibrate in conformity with the frequency of the sound wave.

Changes in atmospheric pressure must have certain characteristics to be perceived, such as exercising sufficient pressure on the eardrum with a certain frequency. If the noise is too soft, it cannot be perceived, but it can be measured with measuring equipment. Some atmospheric pressure changes are not perceived as noise but are experienced physically.

Noise is measured with a microphone. The sound wave also takes along energy, but this energy is relatively small. Noise is often portrayed as a sine wave, but, viewed physically, noise is a longitudinal wave in a medium such as air or water. The wave movement has the same direction as the propagation of the energy. The tops of this wave are the pressure maxima, the valleys of this wave are the pressure minima.

Vibrations caused by a noise source can also travel under water. People and animals, who find themselves under the water surface, can also experience these vibrations as noise. Some fish appear able to perceive noise with their swim bladder.

Sound waves can travel through many materials. The physical phenomenon of sound is studied in acoustics. The experience of sound by people is also studied in psychoacoustics.

What is noise?

Sound

Frequency

Vibration