How does sound wave energy get converted into electricity and why is it less efficient than solar energy?
In: Physics
The microphone reflects *a lot* of the sound energy that hits it. Your simple microphone is like a tiny speaker in reverse where sound hits the diaphragm (little movable plate) and pushes a magnet in and out of a coil of wire. This little diaphragm is hard on the surface which means that a lot of the sound energy hits it and bounces off rather than being absorbed in pushing the magnet through the coil. There are little capacitor based ones but the magnet setup is easiest to understand as a reversed speaker.
Solar panels on the other hand are very absorbant of the frequencies they work with. Some percentage is reflected off the top glass layer but 90% of the light will pass through and then be absorbed down below. The efficiency of solar panels mostly comes down to the sun emitting light over a wide range of frequencies and our little solar panels only being able to absorb a small range of frequencies which is why the best case efficiency of a single junction solar panel is just 37% because that’s the bigger window we can make in the highest energy portion of the sun’s spectrum.
Another issue with capturing sound energy is that there just really isn’t all that much of it. If you were to stand 1 meter away from a jet engine its sound level is around 150 dB, but if you were to capture *all* the sound energy from that jet engine it’d be around 1000 W, a 150 dB sound only gives you 1000 W of energy to work with. You can get that much energy with about 5 m^2 of solar panels and you won’t have a giant turbofan engine screaming away in the background.
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