room criteria (acoustics) (RC)

For evaluating the acoustic quality of rooms and buildings, there is the room criterion (RC) defined by the American National Standards Institute ( ANSI). This is composed of two values, a numerical value and a letter that evaluates the expected spectral quality. The numerical value is the Speech Interference Level( SIL). It corresponds to the arithmetic mean of the sound pressure in the 500 Hz, 1 kHz, and 2 kHz octave bands.

The letter rating is a subjectively determined value, empirically determined from many listeners. It knows as classifications ofsound quality the rating neutral (N), rumbling (R) and hissing (H, hissy) or acoustically induced vibration noise( RV).