Can sound be converted to usable electric energy?

[Omar]

I've had this idea for a while now is it possible to achieve? It's based on the diaphragms in microphones and how they produce weak currents, what if we put huge number of these mics in stadiums and concert halls and connect them with each other's while rectifying the current then amplifying it using transistors?

[Delta1212]

Yes, it's physically possible. Sound really just doesn't carry enough energy for it to be particularly useful, however.

[swansont]

Yes, you can. The main problem is that sound doesn't carry all that much energy, even before you deal with low conversion efficiency.

 

If you yelled at your cold cup of coffee and could capture all the energy with 100% efficiency with no subsequent losses, it would take more than a year to heat it up (details depend on the specific assumptions of how loud a yell is, and how much heating you want to do)

 

http://www.physicscentral.com/explore/poster-coffee.cfm

[Omar]

I know it doesn't carry enough energy and I know we can't get more energy of it than it has but what about amplifying the current by transistors? And what if I use a huge number of microphones and connect them together and put them in places with a great amount of noise like stadiums or concert halls?

[swansont]

I know it doesn't carry enough energy and I know we can't get more energy of it than it has but what about amplifying the current by transistors? And what if I use a huge number of microphones and connect them together and put them in places with a great amount of noise like stadiums or concert halls?

Amplifying the current will not increase the energy, because you'd have to lower the voltage (I assume you mean transformer here)

 

Louder has more energy. But it's still a small value — 100 dB is always going to be 10 mW. Getting to 120 dB only gets you to 1 watt. There no way to get around that fact. We could take 15,000 people and gather their sound output. It would heat up the cup of coffee in the linked example in an hour.

[Omar]

What about the big number of microphones connected together? Doesn't that mean 1 watt from each microphone that takes 120 dB, the more microphones we use the more energy we get?

[swansont]

What about the big number of microphones connected together? Doesn't that mean 1 watt from each microphone that takes 120 dB, the more microphones we use the more energy we get?

 

The calculation in the example already assumes that you're gathering all the energy. If you have 120 dB at the microphone, you have more than 120 dB at the source.

 

Unless you have a source so loud that it causes hearing damage, it's never going to be a lot of energy.

[Omar]

The calculation in the example already assumes that you're gathering all the energy. If you have 120 dB at the microphone, you have more than 120 dB at the source.

 

Unless you have a source so loud that it causes hearing damage, it's never going to be a lot of energy.

I don't need to get the whole watt I was just using an example even if the value is small but the number is huge doesn't that make it usable?

[Greg H.]

So the basic gist is, if you have an hour long football game, you can heat up one cup of coffee with microphones in an hour, of in a couple of minutes with a microwave oven.

 

I think the phrase energy density applies here.

Edited February 24, 2015 by Greg H.

[Omar]

So the basic gist is, if you have an hour long football game, you can heat up one cup of coffee with microphones in an hour, of in a couple of minutes with a microwave oven.

 

I think the phrase energy density applies here.

With one microphone I'm talking about hundreds of thousands of microphones if not millions

[Delta1212]

I don't need to get the whole watt I was just using an example even if the value is small but the number is huge doesn't that make it usable?

Imagine the sound level at a rock concert. It's much louder noise sustained over a longer period than you are likely to get in pretty much any typical environment that you'd rig your system up in. It takes a certain amount of energy for the speakers to produce that much sound over the course of the concert.

 

If you rigged every surface of the concert venue with microphones to capture all of the sound out out by the speakers, the maximum amount of energy that you could possibly generate is less than the amount required to power the speakers.

 

Anything short of covering every surface is going to generate proportionately less energy, and this is assuming much better efficiency in terms of energy conversion than is reasonably practical.

 

So basically rigging up as many microphones you want at an incredibly loud rock concert wouldn't even give you a small fraction of the needed juice to run the speaker system.

[Omar]

Imagine the sound level at a rock concert. It's much louder noise sustained over a longer period than you are likely to get in pretty much any typical environment that you'd rig your system up in. It takes a certain amount of energy for the speakers to produce that much sound over the course of the concert.

If you rigged every surface of the concert venue with microphones to capture all of the sound out out by the speakers, the maximum amount of energy that you could possibly generate is less than the amount required to power the speakers.

Anything short of covering every surface is going to generate proportionately less energy, and this is assuming much better efficiency in terms of energy conversion than is reasonably practical.

So basically rigging up as many microphones you want at an incredibly loud rock concert wouldn't even give you a small fraction of the needed juice to run the speaker system.

You're right but what if we use natural continuous sounds like waterfalls or waves crushing on shores?

[pzkpfw]

Wouldn't you be better off directly harnessing the water? (As is already done).

[Omar]

Wouldn't you be better off directly harnessing the water? (As is already done).

I'm trying to find a new way to get more energy that's it

[Delta1212]

You're right but what if we use natural continuous sounds like waterfalls or waves crushing on shores?

A waterfall is generally somewhat less loud than a typical rock concert. Completely encasing a waterfall in microphones would likely net you even less than my previous example.

[Greg H.]

A waterfall is generally somewhat less loud than a typical rock concert. Completely encasing a waterfall in microphones would likely net you even less than my previous example.

You also run into issues of economics. It's probably going to cost you more to build and maintain such a system than it would be worth based on the amount of energy generated.