SOUND ON BIGGER PLANETS

J

jameswade

Chrono Cadet
I know that there is no sound in outer space because there is no air or gravity but if we were on a planet the size of Jupiter with an atmosphere and other earthly similarity's, would there be a sound to size ratio like there is with weight, the way a person weighs much less on the moon compared to there weight on earth?

For example, A shotgun blast on earth is appx. 140 decibels at 10 feet. Would that same shotgun blast be several hundred decibels higher on a much bigger planet?

What about firecrackers or even a nuclear war heads?
 
james,

For example, A shotgun blast on earth is appx. 140 decibels at 10 feet. Would that same shotgun blast be several hundred decibels higher on a much bigger planet?

What about firecrackers or even a nuclear war heads?
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Not based on size, no. Sound is based on propagation through a medium (in our case on earth, a gas, air). And therefore, for any constant source of sound (which is nothing but a pressure wave), the only thing that can affect it is the medium is travels through itself. All fluid mediums attenuate (lower the amplitude) of a sound that moves through them. The only way you can amplify (the opposite of attenuate) a sound is to actually add energy to that sound. The easiest way to do that is to amplify the sound wave at its source. The other way to do it is much tricker, and that is to add constructive interference within the medium itself such that it amplifies the sound over all the frequencies contained within that sound.

Hope that answers your question.
RMT
 
Thanks rainmantime,

Can you give an example of adding constructive interference within the medium?

what about other forces like explosions, Someone told me once that if you lit a firecracker in your hand on the moon it would blow your arm off, is that true?
 
Can you give an example of adding constructive interference within the medium?
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OK, but because it is tricky I am not sure this will be easy to understand. The "simplest" way to add constructive interference that would amplify a specific frequency in the sound wave would be to add another sound that excites the resonant frequency of the molecules in the medium. By causing the molecules in the medium to resonate, this is adding energy to the medium at that specific frequency. And with the molecules vibrating at this frequency, it would amplify the magnitude of the original sound at that specific frequency. This may help you understand why amplifying the sound at its source is the most practical way to achieve this effect! "Turn it up louder!" :D

what about other forces like explosions, Someone told me once that if you lit a firecracker in your hand on the moon it would blow your arm off, is that true?
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This one is true, and again it is due to the composition of the surrounding medium. In the case of being on the moon, since there is no atmosphere (no gas), then there is no resistance to the explosive force of the fire cracker. But on earth, the atmosphere acts to attenuate the force of the blast (which is also a pressure wave like a sound, but just much much higher pressure differential). So on the moon the mass molecules that make up the explosion would be traveling faster as they travel outwards because there is no resistance from any atmospheric gas. Higher particle velocity striking your hand = greater damage.

But we have a bigger problem which I should address just to be complete: With no atmosphere on the moon I am afraid it would be VERY difficult to get the fuse on a firecracker to light, much less burn. No oxygen to burn! /ttiforum/images/graemlins/smile.gif

RMT
 
would that be like a sound wave passing through an electromagnetic field?
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Since you did not quote the statement of mine you are referring to, it is difficult for me to understand what you mean by "that" (as in "would that be like..."). Can you help a brutha out? /ttiforum/images/graemlins/smile.gif

RMT
 
sorry,

would passing a sound wave through an electromagnetic field add constructive interference that would amplify a specific frequency in the sound wave?
 
would passing a sound wave through an electromagnetic field add constructive interference that would amplify a specific frequency in the sound wave?
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Not in general, no. The only way it could have any effect is if the medium itself is ionized (has a non-neutral charge so it would respond to electric field) or is polarly magnetized so it would respond to the magnetic field. And even then, you are not guaranteed you would amplify the sound.

RMT
 
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