If I add 3 90 decible alarms will it be 270 decibles?
Asked by
XOIIO (
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October 11th, 2009
from iPhone
I was pretty sure that if I wire 3 90 decible alarms together it would be 270 decibles, but a couple people said it wouldn’t. Will it?
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11 Answers
Not completely, its blurs together but not as much as addition. It would probably be around 150 decibles or something.
No, sound levels ar not cumulative. Is one un-amplified guitar one third the sound level of three?
Nope. The decibel scale is a logarithmic scale so doubling the power only results in an increase of about 3dB.
No it would stay the same .
If you and three mates screamed at the same level , it wouldn’t be any louder than just yourself .
@Lightlyseared is correct.
Two buzzers at 90dB summed together is 93dB, the third would add less than 3dB.
@bpeoples woohoo. It had to happen sooner or later.
@DarkScribe IIRC soundwaves in air are a linear system so tripling the sources triples the radiated power. Meanwhile @Lightlyseared is correct.
@Lightlyseared Are you sure about that, on a test I hard to take there was a question about two two guns going off a the same time, the decibels didn’t add together but it was far above an increase of 3 decibels.
@Samurai Yes. The dB scale is a log scale therefore doubling the power of a sound does little to increase the dB. In fact in order to get to the 150dB you sugested in your answer you would have to increase the power by a million times. (10 log 1000000 = 60)
Notably, you also have to watch your phases—if one of the buzzers is 180 to the others (in terms of waveform) it’ll DECREASE the SPL.
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