Quizzes & Puzzles1 min ago
Noise travelling
I'd always thought that someone shouting was a wee bit like throwing a stone : it only went so far & if you were beyond that you wouldn't hear it.
This doesn't explain why you can hear the noise of a football crowd from miles away. If it's too far to hear any of the voices individually, how can we hear the collective noise?
This doesn't explain why you can hear the noise of a football crowd from miles away. If it's too far to hear any of the voices individually, how can we hear the collective noise?
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Your analogy of a stones throw is more analogous to the perception of sound than to the behavior of sound waves.
There is a point where the strength of a sound wave falls below the threshold of audibility but the sound wave continues to propagate outward form the source although at a continuously diminishing strength. Sound waves do not necessarily give up their energy as they travel outward from the source, however their energy is distributed over a wider area as they move outward from the point of origin much as the ripples in a pond formed by a pebble diminish in height as they travel away from the point of impact with the energy being dispersed around a continuously widening circle.
Two or more pebbles dropped together will create a larger wave than one alone and the ripple will travel further before diminishing to the same height as a ripple made by one pebble alone.
Just as two or more pebbles make a bigger wave than one alone, more people talking generate more sound energy than a single person talking. The greater intensity of the sound traveling from an arena of shouting people will travel further before dropping to the level of the threshold of audibility.
As a rule of thumb; one person talking at a distance of one metre has the same apparent loudness of ten people talking at 3 metres or 100 people talking from 10 metres away . . . and when the wind is just right this is why you can hear 10000 eager fans hollering from a mile away.
There is a point where the strength of a sound wave falls below the threshold of audibility but the sound wave continues to propagate outward form the source although at a continuously diminishing strength. Sound waves do not necessarily give up their energy as they travel outward from the source, however their energy is distributed over a wider area as they move outward from the point of origin much as the ripples in a pond formed by a pebble diminish in height as they travel away from the point of impact with the energy being dispersed around a continuously widening circle.
Two or more pebbles dropped together will create a larger wave than one alone and the ripple will travel further before diminishing to the same height as a ripple made by one pebble alone.
Just as two or more pebbles make a bigger wave than one alone, more people talking generate more sound energy than a single person talking. The greater intensity of the sound traveling from an arena of shouting people will travel further before dropping to the level of the threshold of audibility.
As a rule of thumb; one person talking at a distance of one metre has the same apparent loudness of ten people talking at 3 metres or 100 people talking from 10 metres away . . . and when the wind is just right this is why you can hear 10000 eager fans hollering from a mile away.
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