This tool calculates the combined Sound Pressure Level (SPL) due to any number of sources. (Sometimes sound is referred to generically as noise. From that standpoint this also serves as a total noise level calculator).
Enter the levels separated by commas and it will provide the sum total.
SPLTotal = 10*Log10[10SPL1/10 + 10SPL2/10 + 10SPL3/10 … + 10SPLN/10]
The sum of three different souces having noise levels 10 dB, 20 dB and 30 dB is 30.45 dB.
The Sound Pressure Level is measured in deciBel (dB). The Absolute Threshold of Hearing has SPL = 0 dB. By comparison the SPL for a jet engine is 150 dB. The higher the value of SPL the louder the audio level.
A sound level meter shown in the picture below is used to make such measurements in the real world.
It can be used at concert venues, industrial environments and more to make sure the noise levels don’t exceed recommended thresholds.