| Deutsche Version |  |
 |
Adding the level of two uncorreleted (incoherent)
sound sources, like e.g. a violin and a violoncello
| Decibels are logarithmic "units", they may not be added linearly like other figures. If a sound source creates a sound level (SPL) of L1 = 60 dB and another source with L2 = 60 dB is added, then it is not the level of 120 dB, but gives a summing level of 63 dB. If both values are equal, it is easy. More than 3 dB greater than the higher of the two levels is not possible for the total sum in dB. |
Level difference in dB of the levels
The level difference which has to be added to the higher of the two levels
Adding of two levels
Level difference between the two sound sources |
For the sound pressure level of n incoherent radiating sound sources we get: p0 is the reference value of the soundpressure. Auditory threshold at 1 kHz = 0.0002 Pa. Adding of two incoherent sound pressure levels or voltage levels:  Adding of two values of the same level give an increase of the total level of (+)3 dB. This equation is used for electrical adding of incoherent signals, and for the calculation of the enery level of two loudspeakers. Adding of two coherent sound pressure levels or voltage levels:  Adding of two values of the same level give an increase of the total level of (+)6 dB. This is obtained by feeding two side-by-side loudspeakers with the same signal. |
Level adding of up to four sound sources
back  |
Search Engine  |
home  |