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energy of a sound wave

Hi

How do you describe, simply, the energy in a sound wave. If the loudness of sound is the amplitude and the frequency is the pitch then I am assuming, possibly wrongly, it takes more energy to create a louder sound and a higher pitched sound. Or perhaps you can't equate energy to a sound wave like this`

As a sound travels it gets quieter. Is this because the sound has lost energy or it has been absorbed by air/other materials.

Can sound lose pitch as it travels?

thanks

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aburr

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Dave Baldwin

Sound is a pretty mechanical event. The fact that it is often repetitive at a certain frequency makes it seem different but in fact, the whack of a hammer is a sound that doesn't necessarily have a frequency or repetition. Sound get quieter with distance because it loses energy through being absorbed by and air and materials.

Pitch / frequency is set by the mechanical action at the source. I have never heard of pitch being changed by distance itself. Perception is changed by the intensity and if the source moves, the pitch changes at the point of a non-moving observer (Doppler effect).

Dave Baldwin

@aburr is right, I forgot about the square-law effect where the energy density gets lower because the sound spreads out from the source.

andieje

ASKER

'energy density gets lower' is way too confusing for school kids but at least I know the correct terms. School books tend to say 'sound gets quieter as it travels because it is absorbed by other media'
Is it ok to say that as a simplification? I try and observe the correct language where possible.

aburr

"School books tend to say 'sound gets quieter as it travels because it is absorbed by other media'
Is it ok to say that as a simplification?" not really It at least is not untrue
Perhaps you could say that the sound gets quieter because it is spread out over more space.

andieje

ASKER

thank you!