Open Thread, July 16-31, 2012

OpenThreadGuy

If it's worth saying, but not worth its own post, even in Discussion, it goes here.

How exactly is sound additive? I'm having a festival near home (maybe some 2 kilometers away) and I know no individual has the capacity to shout at a volume that reaches my house. But when the 80k people that are watching do it, then it reaches my house. So, how does that happen?

I'm not an expert, but here's what I'd guess:

If 100 people stood exactly the same distance from your house, and sang the same pure note in phase with each other, the resulting sound would arrive with an amplitude 100 times greater than if it was just one person.

If 100 people stood at random distances from your house, and sang the same pure note all with different phases, the resulting sound would arrive with an amplitude 10 times greater.

1billswift14y

Sounds are waves transmitted by air. Waves can reinforce or cancel each other, but cancelling can only go so far (to zero), so what is left is the sound resulting from the reinforced waves.

2Barry_Cotter14y

Not a real answer. Sound is measured in Bels. This is a logarithimic scale. 2 Bels is 10 times as loud as 1, 3 ten times as loud as 2, etcetera. Since sound is a wave I expect the intensity to diminish at constant*(inverse square of distance). Arbitralily say each individual emits 1 unit of sound. 80,000/(2,000^2) = 0.02 Magnitude of arbitrary unit is 0.02 at 2km 80,000 / (1000^2) = 0.08 Magnitude of arbitrary unit is 0.08 at 1km Basically it's an example of an inverse square law. No real understanding of physics was used in this comment.

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Open Thread, July 16-31, 2012

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Open Thread, July 16-31, 2012

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