Sound Power Level and Sound Pressure Level

You have probably heard of ‘Sound Pressure Level’. Often related to what your ears can hear and is most often quantified in decibels. Perhaps you also know that it can be A-weighted to our own hearing?

So far so good, however where a lot of people get lost, is when we add in the definition: ‘Sound Power Level’
Also quantified in decibels and can also be A-weighted to our hearing.

How can you tell the difference?

Sound Power Level:
Quantifies the sound energy that is emitted from a sound-source.
In order to determine the Sound Power Level, one has to measure the Sound Pressure Level in an ‘imaginary’ surface enveloping the sound source, f.ex. a half sphere.

Sound Pressure Level:
Essentially ‘receiving’ the emission caused by the noise source. Most often measured by a microphone (or your ears).