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Oct11-11, 11:25 AM
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That's how a microphone works (moving coil, ribbon etc etc). It transfers mechanical vibrations into tiny electrical signals. But a microphone only gathers a minute amount of sound power and it is not a very efficient transducer in any case. An 'active' system uses energy from a power supply and redirects or absorbs noise energy - an overall loss of useful energy.
Why do people just not bother to do the sums and work out exactly how much energy is available? The actual figures are what count in these matters. What applies perfectly well in principle may not actually apply in practice.

If you invented a machine that would make you 1 penny every minute, it would earn you about 5k a year. Sounds great but if it cost you 10k to build and took 5k a year to maintain, it would be a dead loss. The 'energy from noise' idea is like that but many times worse - more like one penny every hour. You have to get real - particularly if you are thinking of investing your own money.