why are crowds louder than small groups/individuals even if each person produces the same amount of noise? In other words why would a group of people, each generating noise at Xdb sound louder than an individual generating noise at Xdb? How does cumulative sound work?
In: Physics
As others have pointed out, because sound waves can be additive. Your perceived loudness is basically an average of the energy contained in the combined sound waves. One person puts in one person’s worth of sound energy, add another person, and you have two persons worth of sound energy, and so on.
Another way to think of it is with rocks and a calm body of water. Drop one rock in, it makes a small splash. Tape two rocks together, you get a bigger splash, and so on.
It starts to get interesting when you drop the rocks in different places. Then your waves add and subtract in neat patterns, through constructive and destructive interference, which is a fancy way of saying ‘take height of wave a above/below average water level and add height of wave b above/below water level, at specific points. Constructive interference (where both waves are either above or below average water level) = extra high or low wave. Destructive interference (where one wave is above and one is below average water level) = smaller wave or no wave when compared to the originals.
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