a situation in which the loudness of different sounds presented together is the sum of their individual loudnesses. For example, if Sound A at 40 dB SPL (decibels sound-pressure level) has a loudness of 1 sone and Sound B at 50 dB SPL has a loudness of 2 sones, then loudness summation is said to occur if the loudness of A and B presented together is 3 sones. Loudness summation depends on the frequency composition of the sounds. See also critical band.