Støjstyrken

Støjstyrken, often translated as sound intensity, is a physical quantity that expresses the power carried by sound waves per unit area in a direction perpendicular to that area. It is a measure of the energy flow of a sound wave. The SI unit for sound intensity is watts per square meter (W/m²). Mathematically, it is defined as the root-mean-square sound pressure multiplied by the particle velocity, averaged over time. However, it is more commonly related to sound pressure, which is the quantity typically measured by microphones. Sound intensity is a vector quantity, indicating both magnitude and direction of sound energy flow, whereas sound pressure is a scalar quantity. It is important to distinguish sound intensity from sound power, which is the total sound energy radiated by a source per unit time. A sound source emits sound power, and this power spreads out, resulting in a certain sound intensity at different distances. The perceived loudness of a sound is related to sound intensity but is a subjective experience. Sound intensity levels are often expressed in decibels (dB) relative to a reference intensity, commonly the threshold of human hearing. This logarithmic scale is used because the range of sound intensities that the human ear can detect is very wide.