# Converting noise into electrical energy

by kthouz
Tags: convert, electric, energy, noise, piezo
 P: 199 Hello everyone! I have an idea of making a device that can convert noise into electrical energy. In many fields (industries, cars, construction machines,...), some used machines make much noise, then I thought as sound (noise) causes mechanical energy, why not convert that mechanical into electrical energy as microphones do to convert the sound into electrical signals? But here, i would like that device to be more efficient than a microphone. So if anyone worked on the same project or knows something about it that can be helpful, please let me know. Thank you. I will be posting here what i've done so far.
 PF Patron Sci Advisor Emeritus P: 6,203 You should first do an estimate of how much energy is available from the sound noise. I think you will find ridiculously small numbers. And then wonder whether there's any point in making something that can get out this energy.
 Sci Advisor P: 5,403 Also, if the noise is 'noise' (i.e. energy that has been dissipated), there's no way to convert it back into energy available to perform work- 2nd law of thermodynamics. See, for example, Feynman's discussion of the ratchet and pawl.
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## Converting noise into electrical energy

The 2nd law of thermodynamics applies to heat and not noise. Noise can be converted to electricity but I think it's pointless since you would only get very small amounts of electricity.
 Sci Advisor P: 5,403 The 2nd law pertains to entropy. A noisy signal has a different entropy than a coherent signal.
 P: 3,178 I bet you could create some useless gadget like noise powered blinking earrings for the techno-club.
PF Patron
Emeritus
P: 6,203
 Quote by Andy Resnick The 2nd law pertains to entropy. A noisy signal has a different entropy than a coherent signal.
Yes, but I think what you are referring to is "thermal acoustic noise", and a noisy machine has quite more noise than the thermal noise which is limiting sound registration for instance. This is like white light, which is also electromagnetic noise, but if its energy density is larger than the thermal (black body) electromagnetic noise (radiation), you can still extract energy from it (with photovoltaics, for instance).

However, the energy of acoustic noise, even if it is "loud", is still quite small, so, it would not be very useful (but the earrings might be an idea )
 P: 3,394 I would foremost consider a magnetic damper (e.g., a magnet and a coil mounted on relatively vibrating surfaces) that generates current. Also, a putative model for a Maxwell's demon, of which there are many applied to "thermal acoustic noise," could more realistically be modified to your purpose.
 PF Patron Sci Advisor P: 1,373 [QUOTE=kthouz;2354498]Hello everyone! I have an idea of making a device that can convert noise into electrical energy. better yet, convert noise into MONEY Dire Straights did a song..Money for Nothing and Chicks for free.... seriously..i applaud your idea
P: 5,403
 Quote by vanesch M This is like white light, which is also electromagnetic noise, but if its energy density is larger than the thermal (black body) electromagnetic noise (radiation), you can still extract energy from it (with photovoltaics, for instance).
That's a really excellent analogy, thanks!
 P: 199 Thanks for your ideas. That was my idea too, and i did consider the electrical signals collected by a microphone which have to be amplified in order to be put through speaker, noise should not be really efficient to give an important electrical energy. But, meanwhile, i have been googling and i found a device that has been made "sonea" which is used to convert noise of huge machines into electricity. Anyway, i will still looking for another thing to work on (related to physics specially material physics or renewable energy"? Is anybody got something else, please let me know.
 P: 1 Lads great idea with the noise.... I work for a roads dept and am currently looking into this... we were looking at noise mitigation noise barriers... and decided to take it one step further and maybe steal some energy if possible... the "sonea" website was a great start thanks for that kthouz... these roads would be busy 30,000 vehicles per day with noise levels on properties of around 70dB peak times... so represent a way of capturing energy from the traffic... Is this a feasible idea or am i just wasting my time in terms of energy generation?
 PF Patron Sci Advisor P: 10,076 A tiny fractional increase in the efficiency of the original acoustic noise source would represent much better use of the original energy source.
 P: 2 i think this idea for producing energy may be feasible but it can be better in removing noise energy. i am working on noise cancellation and i think by converting noise into electrical energy it can be removed by filters.anyway good luck for your work.
 PF Patron Sci Advisor P: 10,076 The flux of sound energy at the threshold of hearing is 10-12 W / m2 If the sound levels you are dealing with are, say 80dB, that means you would expect only 0.1mW of energy for every square metre of any system used for collecting this noise energy. I think that gets things in proportion. It may be 'almost deafening' but there ain't much actual energy available. Even at the 'threshold of pain (120dB), you'd only get 1W per sq m.. Compare that with a solar cell in cloudy conditions in Winter - and a solar cell is giving you actual electrical power - your sound energy reclamation device would still have to do some energy conversion to electrical, with I've no idea what efficiency.
 P: 2 i dnt want to convert noise into electrical energy for reproducing energy. But if i convert noise into electrical form than i can use some electronics things to remove noise. My application of this conversion is for removing noise in apartments or dense area which generally comes from window so i want to make something which removes noise with opened window.thanks for reply.
 P: 10 can sum1 give or enlighten me with "sonea". we have a feasibility study and our topic is about harnessing sound energy to electrical energy.we are having a hard time but we cant back up now.can sum1 help me with this topic?any1 there who could help me plz do
 P: 1,284 It's hard to tell you, since the only info about the "sonea" in the english language was written by someone who doesn't know what a dB is and who confuses power and energy.

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