D

Damping
The dissipation of sound energy by sound dissipative properties of a structure or material.

Dead Room
A room containing an unusually large amount of sound absorption.

Decay Rate
The rate at which the sound level in a room decreases with time, after the sound source is turned off. Its unit is dB per second.

Decibel (dB)
A basic metric for describing the magnitude of sound. A division of a uniform scale based upon 10 times the logarithm to the base 10 of the relative value being compared (sound intensity, pressure squared, or power) to a specified reference value.

Diffraction
The ability of a sound wave to “flow” around an obstruction or through openings with little loss of energy.

Diffusion
Dispersion of sound within an enclosure such that there is uniform energy density throughout the space.

Direct Sound
A sound field produced and dominated by the sound waves emanating directly from a source, also referred to as the “near field.”

Discrete Frequency
A sound source in which sound exists only at one or more individual frequencies. The opposite of discrete in acoustical terminology is ‘continuous.’

Dynamic Range
The range in decibels between the maximum and minimum signal levels from a device or sound source.