Power and Intensity

The sound waveform illustrates the time evolution of pressure variations. Related to pressure is:

sound power emitted by the source:
- a fixed quantity (measured in watts, W);
- analogous to the wattage rating of a light bulb.
$\includegraphics[scale = .45]{eps/lightbulbPowerB.eps}$
sound intensity a distance from the source:
- power per unit area carried by wave (W/m);
- influenced by interference from environment;
- akin to brightness of a light at a point in room.

$\includegraphics[scale = .55]{eps/lightIntensity.eps}$

``Music 171: Sinusoids'' by Tamara Smyth, Department of Music, University of California, San Diego (UCSD).