Is sound energy useful as a source for generating electricity? If so, could it be a renewable resource?
closed as unclear what you're asking by John Rennie, Norbert Schuch, ACuriousMind♦, Daniel Griscom, JamalS Jan 22 '16 at 22:28
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I think you might be a little confused.
The phrases 'renewable energy' and 'un-renewable energy' are used to refer to industrial sources of energy. These industrial sources include Wind, Solar, Wave, and Nuclear power, and traditional fossil fuels (coal, oil, natural gas etc.).
If a source of power is renewable, it is not depleted (used up) when utilised - for example, the wind doesn't run out just because you put a few turbines up.
These industrial sources are not forms of energy themselves - they produce energy (heat energy like in a nuclear reactor or kinetic energy like in wave and wind power), but "solar power" or "wind power" are not a forms of energy. They are sources. This link gives a good overview of the different forms of energy.
Sound energy is associated with the vibrations of matter (sound waves vibrate air particles - that's how you can hear), so is a form of kinetic energy (the energy all things have when they move). It is not an energy source, so it doesn't make sense to call it "non-renewable" or "renewable".
Sound could be considered a renewable resource if taken from a source that was created by continual physical processes - such as the sound of waves crashing against rocks.
Although those sound waves contain energy (which is the kinetic energy of moving/vibrating air particles), their energy density is very low. Therefore they are not useful for generating electricity. This answer from MIT school of engineering will give you some idea of their relative power:
What the human ear perceives as clanging cacophony — the roar of a train engine or the whine of a pneumatic drill—only translates to about a hundredth of a watt per square meter. In contrast, the amount of sunlight hitting a given spot on the earth is about 680 watts per meter squared
If we were to assume that ocean waves created the same quantity of energy as stated here for pneumatic drills and train engines, then to get a similar energy as 1 metre squared of solar panels, you would need 'sound panels' that equaled a total area of 62,000 metres (62 kilometres) squared. However, these sound panels would then have to be very close to the source of sound to be most efficient, as sound energy is not transferred through air efficiently at all. To solve this, lets say we made them 1 metre high. In this case, to equal the energy available to 1 metre squared solar panel in full light, you would need 1 metre high sound panels that stretched along 3,844kms of rocky coastline. You see, not very practical at all!
I think there is a problem in your question, cause "sound" is a phenomena in the meaning of process. When we talk about renewable energy, we in fact generally discuss sources (E.g. sun, not EM waves).
Straightforward and basically there are two, mostly engineering problems:
- Sound is a mechanical wave of a very low energy compared to industrial processes scales.
- What is the "natural" source of such waves that could be used in the meaning of "mining, collecting etc."
Little for fun thermodynamics note: Usual aeroacoustical linear approximation says that acoustical flow is homentropic. That means no heat transfer and therefore no entropy increase. It's not the "renewability", but at least the sound does not feed the beast of entropy much. :-)