To use this form, simply fill-in the Source Level 1 and Source Level 2 fields, then click "Calculate".
The answer will appear in the Output Level field.

Adding Decibels
Source Level 1 (dB) 
Source Level 2 (dB) 
Output Level (dB) 
Important: The decibel calculator can be used to combine the sound levels of two sound sources when the level of each source is given in decibels (dB). The calculator can be used to combine any "like quantity" that is expressed in decibels. For example, you can combine two A-weighted sound levels, or two octave band sound levels, or two 1/3-octave band sound levels, or two un-weighted sound levels. However, you cannot combine unlike quantities (e.g. one A-weighted sound level and one un-weighted sound level, or one sound power level and one sound pressure level). The only additional restriction is that the two sounds must be incoherent. Most noise sources are random and incoherent, but some are not. The most common example of a coherent sound is a sound that contains a strong pure tone.