How does SPL decrease with distance?

In free-field conditions, SPL drops by 6 dB for every doubling of distance (inverse square law). So if a speaker produces 100 dB at 1 metre, it produces 94 dB at 2 metres, 88 dB at 4 metres, and so on. Indoors, reflections reduce this loss.

How does power affect SPL?

Doubling the power adds +3 dB. So to increase SPL by 10 dB (perceived as twice as loud), you need 10× the power. Going from 10W to 100W adds 10 dB; going from 100W to 1000W adds another 10 dB.

What SPL levels are typical for different events?

Background music: 70-80 dB. Small gig/bar: 90-100 dB. Concert: 100-110 dB. Festival front of house: 105-115 dB. UK noise at work regulations limit exposure to 85 dB over 8 hours (daily average).

What is the inverse square law?

The inverse square law states that sound intensity decreases proportionally to the square of the distance from the source. In dB terms: SPL loss = 20 × log10(distance). This assumes free-field conditions with no reflections.

AudioCalcs

SPL Calculator — Sound Pressure Level at Distance

Calculate sound pressure level at distance from speaker sensitivity and power.

Speaker Sensitivity

Amplifier Power

Distance

How We Calculate This

SPL at 1 metre

SPL (1m) = Sensitivity + 10 × log10(Power)

SPL at Distance

SPL (d) = SPL (1m) − 20 × log10(distance)

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates based on standard formulas. Always verify results for critical applications.