According to the inverse square law, what happens to SPL when the distance to a sound source is doubled?

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Multiple Choice

According to the inverse square law, what happens to SPL when the distance to a sound source is doubled?

Explanation:
When distance doubles, the sound energy spreads over four times as much area, so the intensity drops to one-quarter. Since sound pressure is proportional to the square root of intensity, the pressure becomes one-half of its original value. SPL uses 20 log10 of the pressure ratio, so a halving of pressure gives 20 log10(1/2) ≈ -6 dB. Therefore the sound level decreases by about 6 dB. The other options don’t match this physical spread: they would imply different pressure or intensity changes that aren’t produced by simply doubling the distance.

When distance doubles, the sound energy spreads over four times as much area, so the intensity drops to one-quarter. Since sound pressure is proportional to the square root of intensity, the pressure becomes one-half of its original value. SPL uses 20 log10 of the pressure ratio, so a halving of pressure gives 20 log10(1/2) ≈ -6 dB. Therefore the sound level decreases by about 6 dB. The other options don’t match this physical spread: they would imply different pressure or intensity changes that aren’t produced by simply doubling the distance.

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