[bvk]

bvk asked the Naked Scientists:
   
With what device can we convert sound energy into electrical energy?

What do you think?

[Geezer]

It sounds a bit homeworky  []

[Pumblechook]

A speaker ..bigger the better.

[graham.d]

Well, a speaker working backwards, Pumblechook, or what we would normally call a microphone :-)

[techmind]

And you won't be generating enough energy to save the planet [], nor even to power a puny little LED  []

Teeny tiny amount of energy - need to connect it to an electronic amplifier to do much useful with it.

[RD]

... you won't be generating enough energy to save the planet [], nor even to power a puny little LED  []

*ahem* ...

[Pumblechook]

Tapping with a figure aint hitting it with sound.

Microphones produced very low level output and have to be amplified.

Old fashioned microphones in telephones were vastly more sensitive but they didn't produced an electrical output but were variable resistance,, Carbon Mics.

[Geezer]

How about a room where the walls are constructed of electrostatic speakers?

I suppose it would depend on how efficient they were.

[RD]

Tapping with a figure aint hitting it with sound.

Sound can be surprisingly powerful ...

[graham.d]

I didn't see any hint in the question that there was intent to produce energy for any specific usage. Why has this been assumed? The question is about converting sound energy into electrical energy (e.g. a microphone), not trying to power anything from it, other than as a signal source to other electronic equipment.

[Geezer]

I didn't see any hint in the question that there was intent to produce energy for any specific usage. Why has this been assumed? The question is about converting sound energy into electrical energy (e.g. a microphone), not trying to power anything from it, other than as a signal source to other electronic equipment.

That's true, although we'd probably have to be careful about the particular type of microphone, because some of them don't convert sound into elecrical energy.

[graham.d]

That's true, although we'd probably have to be careful about the particular type of microphone, because some of them don't convert sound into elecrical energy.

Really? I thought that this was a definition of "microphone" - at least a working one. Please explain.

[Geezer]

That's true, although we'd probably have to be careful about the particular type of microphone, because some of them don't convert sound into electrical energy.

Really? I thought that this was a definition of "microphone" - at least a working one. Please explain.

Some microphones, like moving coil microphones for example, convert sound energy into electrical energy. Other microphones, like certain types of condenser microphones for example, do not. They modulate a current or voltage to produce a signal, but they do not convert sound energy into electrical energy.

[graham.d]

Pedantry, my dear fellow. I would say that you are producing electrical energy even to modulate an electric current (allbeit a very small amount). In any case what emerges from the microphone is electrical energy even if you have to supply a power source. I think most definitions of microphone say that it is a device that converts sound into electrical energy - the efficiency can be less that one or, in the case where you supply power, it may (or may not) be greater than one. In either case, there is sound energy going in and an electrical representation of this sound energy coming out.

[Geezer]

Not pedantry - simply scientific precision.

Actually, Wiki (for what it's worth) describes a microphone as something that can convert sound into an electrical signal, which I agree with. However, unless a microphone produces electric power without an external power source, I don't think we should say it's converting sound energy into electrical energy, although that really depends on how we define "convert".

Anyway, if you think we'll be able to convert mechanical energy into electrical energy by wiggling a potentiometer, we could be in the money!