Required Voice Level at Distance
Distance and perception of voice.
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:
| Distance | Voice Level (dB PSIL) | ||||
|---|---|---|---|---|---|
| (ft) | (m) | Normal | Raised | Very Loud | Shouting |
| 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) (1)
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.
