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  1. 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 ( P1 and P2 ) 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 ✎

    1. How many decibels correspond to doubling the pressure of a sound?

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

    3. What does 0 decibels mean?

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

10 log(2) ≈ 3.0

P = 20 · 106 = 2 · 107

The sound ratio is 1.

100 times more pressure.