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# SIL - the Speech Interference Levels

## Background noise frequencies that interferes with speech.

Speech Interference Levels - SIL - are arithmetic average sound pressure levels at the 500, 1000 and 2000 Hz center frequencies - and a measure of the degree to which background noise interferes with speech.

• 1 ft = 0.3048 m

The diagram above indicates the SIL and the distance at which a person would have talk in a normal, raised, very loud or shouting voice to be understood.

### Example - Use of Voice with Background Noise

If the background noise - sound pressure level - is 75 dB and the distance between two persons is 6 m - they have to raise their voice to more than a very load level according the diagram above.

## Related Topics

• ### Acoustics

Room acoustics and acoustic properties, decibel A, B and C, Noise Rating (NR) curves, sound transmission, sound pressure, sound intensity and sound attenuation.

## Related Documents

• ### Decibel

Logarithmic unit used to describe ratios of signal levels - like power or intensity - to a reference level.
• ### Noise - EPA Protective Levels

The noise level should not exceed certain values to protect public health and welfare.
• ### Noise - Maximum Daily Dose Level

Maximum daily noise dose level when exposed to periods with different levels.
• ### Noise Criterion vs. Noise Rating and dB(A)

Comparing Noise Criterion (NC, NCB, RNC) to Noise Rating (NR) and dB(A).
• ### Outdoor Ambient Sound Pressure Levels

Outdoor ambient sound pressure levels (dBA) in rural and urban business and industrial environments with or without limited traffic.
• ### Sound Level - Online Calculator

Calculate sound level, pressure and intensity.
• ### Sound Power

Sound power from sources like fans, jet engines, cars, humans and more.
• ### Sound Pressure

Sound Pressure is the force of sound on a surface perpendicular to the propagation of sound.
• ### Use of Telephones in Noisy Areas

Satisfactory, difficult and impossible noise levels for telephone use in noisy areas.

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## Citation

• The Engineering ToolBox (2008). SIL - the Speech Interference Levels. [online] Available at: https://www.engineeringtoolbox.com/speech-interference-levels-d_1138.html [Accessed Day Month Year].

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12.8.9