Soundproofing glossary definition of SPEECH-INTERFERENCE LEVEL (SIL)

SPEECH-INTERFERENCE LEVEL (SIL) :

A calculated quantity providing a guide to the interference of a noise with the reception of speech. The speech-interference level is the arithmetic average of the octave band levels of the interfering noise in the most important part of the speech frequency range. The levels in octave bands centered at 500, 1000, and 2000 Hz are commonly averaged to determine the speech-interference level.