Definitions

Decibel
A logarithmic measure of the ratio of sound levels, as used in describing levels of sound pressure or sound power, usually related to a reference level.

Diffraction
The bending of sound waves around an obstacle or barrier.

Frequency
The number of cycles per second measured in units of Hertz. A frequency of 1000 Hz means 1000 cycles per second.

Leq
The equivalent steady level that would produce the same A-weighted sound energy over a stated period of time as varying sound level over that period.

Octave Band
A frequency band with an upper frequency limit equal to twice the lower limit.

Sound Absorption Coefficient
The ratio of the sound energy absorbed by a material to the energy incident upon it.

Sound Reduction Index
The sound reduction index of a structure is the insulation value of that structure expressed in decibels.

Sabins
The amount of sound absorption provided by a product or system, equal to its sound absorption coefficient times its surface area, measured in sabins.