
Ask HN: sound - electricity? - jibiki
I was thinking about doing a little wind power project, and thought it would be cool to not use a turbine... so, what's a cheap and easy way to generate electric power from sound?  (Maybe using those little piezoelectric buzzers?)
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J_McQuade
When it comes to power from sound, be warned that results are likely to be
rather disappointing - there's a reason microphones and guitar pickups benefit
from such highly sensitive pre-amps! If you're just looking to do it out of
intellectual curiosity, though, then piezos will at least get you somewhere -
like DC motors, they're a 'two-way' thing; put power in, get vibration
(sound), put in vibration, get (a little) power. You can often scrounge them
from old toys, too, so they might be worth a look.

Other than that, there are a few interesting projects out there looking at
alternatives to turbines for generating wind energy - my favourite would have
to be this one:

[http://www.popularmechanics.com/technology/industry/4224763....](http://www.popularmechanics.com/technology/industry/4224763.html?series=37)

Cobbling one of those things together could make for an interesting and fairly
cheap project - if you find the time to do it then I'd love to see the 'vital
statistics' of how much juice it'll give you!

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jibiki
Thanks, that looks awesome. It's hard to find any good guides online
(wikipedia links to one that makes no sense at all) but it seems like an easy
project to do without instructions, since all it takes is a couple solenoids
and a magnet or two.

Just experimenting with paper strips, it seems like the frequency depends on
the width between the membrane and the base. Does anyone know if/why this is
true?

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electromagnetic
I'd say, depending on your scale, the best power generation you're going to
get out of sound would be to use a very large and light membrane to catch the
sound and tie it to piezoelectric cells.

You want to produce the maximum deflection possible on the piezoelectric cells
as this will produce the largest amount of electrical energy. This will
probably be cheaper to do by connecting something like a mylar sheet (a cheap
place to look would be the foil wrapping-paper at the dollar store) to some
piezoelectric cells.

I'm unsure if piezoelectric cells alone would receive enough force to produce
a noticeable effect.

An alternative would be to produce a very large cone and place a piezoelectric
cell in the tip of the cone. This would perhaps be a lot less work. However I
have a greater understanding of electrics than acoustics, so I'm unsure if it
would be better to channel the sound to a small surface or to simply use a
large lightweight membrane.

Hopefully this helps you some.

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ars
Wind essentially IS sound - but with a very low frequency.

Sound is air moving, wind is air moving.

You can use a turbine that spins forward and back I suppose. You'll have a
hard time with this - you'll need to match your turbine to the frequency of
the sound. Using a microphone works, but only for frequencies in human range.

If you want to catch more energy you'll need to handle infra-sound. Meaning a
massive microphone.

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shaunxcode
You may want to check out this guys work:
<http://www.unews.utah.edu/p/?r=053007-1> "heat -> sound -> electricity"

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drhowarddrfine
I had not thought of this and I congratulate you on being so clever to think
this up. I don't know if it would work but it's well worth considering.

