How much is sound pressure reduced every time the distance from the source is doubled?

The correct answer is based on the understanding of the inverse square law in acoustics. When the distance from a sound source is doubled, the sound pressure level decreases due to the spreading of the sound wave over a larger area. This phenomenon occurs because sound energy distributes itself uniformly over the surface area of an expanding sphere, and as you double the distance, the increase in surface area results in a reduction in sound intensity.

Specifically, the sound pressure level decreases by approximately 6 dB each time the distance from the source is doubled. This is derived from the relationship between sound intensity (which is proportional to the square of the sound pressure) and distance. When distance is doubled, the intensity diminishes to one-fourth of its original value, which corresponds to a decrease of 6 dB on the decibel scale. Thus, the principle behind this calculation is fundamental to understanding how sound behaves in an environment and is essential for acousticians and audio engineers when designing sound environments.