Sound intensity level

Definition

Sound intensity level is a logarithmic measure of the sound power per unit area. It is measured in decibels (dB) and compares the intensity of a sound to a reference level.

5 Must Know Facts For Your Next Test

1. The formula for sound intensity level is $L_I = 10 \log_{10}(I/I_0)$, where $I$ is the sound intensity and $I_0$ is the reference intensity, typically $1 \times 10^{-12}$ W/m².
2. Sound intensity level is always expressed in decibels (dB).
3. A doubling of the sound's power increases its intensity level by approximately 3 dB.
4. Human hearing ranges from about 0 dB (threshold of hearing) to around 120-140 dB (threshold of pain).
5. Sound intensity level allows for easier comparison between vastly different levels of sound energy.

Review Questions

• What units are used to measure sound intensity level?
• How does doubling the power of a sound source affect its intensity level in decibels?
• What is the typical reference intensity ($I_0$) used in calculating sound intensity levels?

Related terms

Decibel (dB): A unit used to measure the intensity of a sound or the power level of an electrical signal by comparing it with a given level on a logarithmic scale.

Threshold of Hearing: The quietest sound that can typically be heard by a young, healthy human ear, usually defined as $0$ dB or $1 \times 10^{-12}$ W/m².

Logarithmic Scale: A nonlinear scale used for a large range of quantities where each tick mark on an axis is a constant factor larger than the previous one.