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Required Voice Level at Distance

Talking with

• a normal voice approximates to a sound pressure level of 70 dB
• a raised voice approximates to a sound pressure level of 76 dB
• a very loud voice approximates to a sound pressure level of 82 dB
• a shouting voice approximates to a sound pressure level of 88 dB

at a distance of 1 ft (0.3 m).

For every doubling of the distance from the noise source the sound pressure level decrease with 6 decibels:

Required Voice Level at Distance
DistanceVoice Level (dB PSIL)
(ft)(m)NormalRaisedVery LoudShouting
1 0.3 70 76 82 88
3 0.9 60 66 72 78
6 1.8 54 60 66 72
12 3.7 48 54 60 66
24 7.3 42 48 54 60

PSIL - Preferred Speech Interference Level - is the arithmetic mean level in the 500 Hz, 1 kHz and 2 kHz octave bands. PSIL simulates the fact that sounds in the speech frequency range by humans are rendered indistinguishable from non-speech sources by excessive noise levels.

PSIL can be calculated as

PSIL = 1/3 (Lp500 + Lp1000 + Lp2000)

where

PSIL = Preferred Speech Interference Level (dB)

Lpx = sound pressure at frequency x (dB)

dB calculated with reference pressure 2 10-5 Pa

If sound pressure is known in dBA - PSIL can be calculated as

PSIL = Lp (dBA) - 7

In social settings people often talk with normal voice levels at distances ranging 1 to 4 metre. In such cases background noise levels should not exceed 55 to 60 dBA.

In outdoor play and recreational areas people often communicate with raised or very loud voices at distances 5 to 10 metre and the background noise should not exceed 45 to 55 dBA.

Related Topics

• Acoustics

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

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Doubling of the distance from a noise source reduces the sound pressure level with 6 decibel.

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