By: Tao Steven Zheng (鄭濤)

The decibel (dB) is a measure of the ratio between two quantities, and is used in a wide variety of measurements in acoustics. The decibel is used for measuring of the loudness of sound.?

【Problem】

A police car siren measures 70 dB to someone 44 meters away. What is the sound level of the police car if the police car is 1 meter away from the person? Round to the nearest decibel.

【Solution】

There are two formulas that are useful for this problem：

1) where

2)

First, solve for the intensity at 44 meters.

Second, solve for the power, which is the same at any distance away from the sound source.

Third, solve for the intensity at 1 meter.

Lastly, calculate the sound level in decibels.