Inverse Square Law

Useful when setting up a microphone or speaker, the inverse square law states that, in a free field the intensity of sound drops by 6 dB for each doubling of distance from the source. Now, none of us ever work in a truly free field (no reflective surfaces), but for most applications these numbers are accepted as workable. In real world terms, this means that for each time you double the distance between your sound source and a listener or microphone, the power of the audio drops by 75% – a fairly significant amount! How much is this in terms of volume? Well, it depends on the source you consult, we’ve seen both 6 dB and 10 dB convincingly listed as doubling or halving the volume (let’s just say it’s subjective and leave it at that…) – regardless, 6 dB is a very noticeable drop in level! Consider this the next time you place a microphone or speaker: Rather than just cranking up or attenuating the mic preamp or amplifier level for gain control, look at the distance to your source…