Speech Interference Level
The Speech Interference Level (abbreviated to SIL, in German roughly “ Speech Impairment Size”, but a German technical term is not in use) is an acoustic parameter that is intended to describe the impairment of speech intelligibility due to background noise .
The SIL is formed as the arithmetic mean of the linear sound pressure level in selected octave bands .
Two variants of the SIL are common:
- SIL3: The arithmetic mean of the linear sound pressure level in the 1 kHz , 2 kHz and 4 kHz octaves
- SIL4: The arithmetic mean of the linear sound pressure levels in the 500 Hz , 1 kHz, 2 kHz and 4 kHz octaves.