### Home > CCA2 > Chapter 11 > Lesson 11.2.1 > Problem 11-49

11-49.

Logarithms are used to measure the “loudness” of sound. Decibels (dB) are logarithmic units used to describe a ratio of two levels of intensity or pressure. The difference between two levels of sound pressure (

*P*_{1}and*P*_{2}) is defined as 10 log()dB. Usually, when decibels are used to describe just one sound, it is assumed that that sound is being compared to a reference level of 20 micropascals. Homework Help ✎ How many decibels correspond to doubling the pressure of a sound?

What is the sound pressure of a noise described as 60 dB?

What does 0 decibels mean?

How many times more pressure is in a sound of 40 dB than of 20 dB?

10 log(2) ≈ 3.0

*P* = 20 · 10^{6} = 2 · 10^{7}

The sound ratio is 1.

100 times more pressure.