How are decibel sound levels added?
If there are two uncorrelated sound sources in a room – for example a radio producing an average sound level of 62.0 dB, and a television producing a sound level of 73.0 dB – then the total decibel sound level is a logarithmic sum i.e. Combined sound level = 10 x lg ( 10^(62/10) + 10^(73/10) ) = 73.3 dB Note: for two different sounds, the combined level cannot be more than 3 dB above the higher of the two sound levels. However, if the sounds are phase related (“correlated”) there can be up to a 6dB increase in SPL.
