Decibel Combine Calculator

About this calculator

Sound levels in decibels (dB) are logarithmic, so they can't simply be added together — combining two sources requires converting each back to sound intensity, adding the intensities, then converting back to dB: L = 10 · log₁₀(10^(L₁/10) + 10^(L₂/10)). Two equal sound sources don't double the decibel reading; they only add about 3 dB (e.g. two 70 dB machines running together produce about 73 dB, not 140 dB), because decibels measure intensity on a logarithmic power scale.

Acoustic engineers, audio engineers and occupational health/safety professionals use decibel combination constantly: predicting the combined noise level of multiple machines on a factory floor, calculating total sound pressure when several loudspeakers play simultaneously, or estimating cumulative environmental noise from multiple sources (traffic, HVAC units, industrial equipment) for regulatory compliance and hearing-protection planning.