Estimating Sound Levels With the Inverse Square Law

In the real world, the inverse square law is always an idealization because it assumes exactly equal sound propagation in all directions. If there are reflective surfaces in the sound field, then reflected sounds will add to the directed sound and you will get more sound at a field location than the inverse square law predicts. If there are barriers between the source and the point of measurement, you may get less than the inverse square law predicts. Nevertheless, the inverse square law is the logical first estimate of the sound you would get at a distant point in a reasonably open area.

If you measure a sound level I1 = dB at distance d1 = m = ft then at distance d2 = m = ft the inverse square law predicts a sound level I2 = dB 如果你在距离 d₁ = m = ft 处测得声电平 I₁ = dB，那么根据反平方定律，在距离 d₂ = m = ft 处预测的声电平 I₂ = dB 中文译文中的待填/计算数值依次对应：1：i1 2：d1 3：d1c 4：d2 5：d2c 6：i2。实际数值以上方原输入框为准。

You can explore numerically to confirm that doubling the distance drops the intensity by about 6 dB and that 10 times the distance drops the intensity by 20 dB.