Sound Power


Sound power or acoustic power Pac is a measure of sonic energy E per time t unit. It is measured in watts and can be computed as sound intensity (I) times area (A):

P_{\mathrm{acoustic}} = I \cdot A

When the acoustic wave approaches the measurement surface at an angle, the area is taken as the area times the projection of the wave direction upon the normal of the surface.

The difference between two sound powers can be express in decibels (logarithmic measure) using this equation:

L_\mathrm{w}=10\, \log_{10}\left(\frac{P_1}{P_0}\right)\ \mathrm{dB}

where, are the sound powers. The sound power level SWL, LW, or LPac of a source is expressed in decibels (dB) relative to a reference sound power. In air this is normally taken to be = 10−12 watt, that is 0 dB SWL.

Unlike sound pressure, sound power is neither room dependent nor distance dependent. Sound power belongs strictly to the sound source. Sound pressure is a measurement at a point in space near the source, while sound power is the total power produced by the source in all directions.

Read more about Sound Power:  Table of Some Sound Sources, Sound Power Measurement, Sound Power With Plane Sound Waves, Sound Power Level

Famous quotes containing the words sound and/or power:

    “Only the sound remains,
    the distant thump of the good elephants,
    the voice of the ancient lions
    and how the bells
    trembled for the flying man.”
    —Anne Sexton (1928–1974)

    “None who have always been free can understand the terrible fascinating power of the hope of freedom to those who are not free.”
    —Pearl S. Buck (1892–1973)