Reflected sound intensity is reduced in proportion to the absorption coefficient

Evidence

How does the absorption of sound affect the level of early reflections heard by the listener? The absorption coefficient of a material defines the amount of energy, or power, that is removed from the sound when it strikes it. In general, the absorption coefficient of real materials will vary with frequency, but for the moment, we shall assume it does not. The amount of energy, or power, removed by a given area of absorbing material will depend on the energy, or power, per unit area striking it. As the sound intensity is a measure of the power per unit area, this means that the intensity of the sound reflected is reduced in proportion to the absorption coefficient. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1719

In general, most surfaces absorb some of the sound energy, and so the reflection amplitude is weakened by the reflecting surface. Therefore, the level of direct reflections will be less than that which would be predicted by the inverse square law due to surface absorption. The amount of energy or power removed by a given area of absorbing material will depend on the energy or power per unit area striking it. As the sound intensity is a measure of the power per unit area, this means that the intensity of the sound reflected is reduced in proportion to the absorption coefficient. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2316

Categorization

• DEFINE: Defines the absorption coefficient as the fraction of sound energy removed when it strikes a material.
• XREF: Builds on the inverse square law and absorption coefficient material from earlier chapters; this is the synthesis step. — connects to: Diffusing early reflections lowers their level without absorbing the sound energy — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2315
• corroborated: 2 independent passages support this claim — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1719; David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2316