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There are a lot of ideas on here about harvesting tiny
bits
of spare energy with the snag of the energy not being
enough to achieve very much. I don't consider this idea
to
fall into that category.
Psychoacoustic compression filters out most audio data
without intrusive compression artifacts.
Most of these
are
probably irrelevant to the energy question, but not all.
For
a start, there must be a lot of ultrasonic and infrasonic
sound which currently serves no purpose at all but could
be
detected by a microphone, and the likes of a quiet noise
just before a louder one or masked by a louder one can
safely be removed from a recording without listeners
noticing. Moreover, noises at night, such as traffic,
ticking alarm clocks, snoring, central heating boilers and
fridges turning on and off and so forth, are if anything a
nuisance to people with good hearing. For a hearing aid,
sitting unused by the bedside, they are also wasted
energy.
Therefore, why not use the energy of these sounds to
recharge the hearing aid? Store them in a capacitor,
maybe, and release that into the battery when it runs
low.
No more need to change batteries as often.
Oh, and the reason why i think it's more practical for this
device than others is that a hearing aid needn't use
much power.
Hearing aid power consumption
http://www.maxim-ic...s/index.mvp/id/4691
"1-10 mW" [csea, Oct 28 2011]
Sound Power
http://en.wikipedia.org/wiki/Sound_power
Sound power vs SPL [csea, Oct 28 2011]
Piezo powered.
http://www.noliac.c...efault.aspx?ID=5091
No mention of using sound or not. [2 fries shy of a happy meal, Oct 28 2011]
[link]
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Hmm, let's look at a few back-of-the envelope numbers. |
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From a chip manufacturer, we see that hearing aids typically consume 1-10 mW of power. [link1]
And the sound power of various sources seems also in that range (including "vivid children!"). [link2] |
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The difficulty lies in the dispersal of that power over volumetric distance and the surface area of a collector used to capture the power. At 1 meter distance from "vivid children," the 1mW of power is distributed over 4(pi)R^2 meters, or about 12 square meters. If we hope to capture energy with a small diaphragm, say a 1 cm square, the most we could hope for is 1/1200 of a mW, or 833nW (nanowatts.) Rounding up to a microwatt, we're still shy by a factor of 1000 to 10,000. |
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The clear answer is 5000 vivid children slaves driven to louder wailing by whips, so you can just turn the hearing aid off altogether. |
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I did have a thought about including an ear trumpet.
Then you could throw away the hearing aid
altogether. |
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How about a tiny dynamo rigged to a self-winding watch
mechanism? |
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How about one of those kinetic battery chargers?
It would need to be quite small, and would need
quite vigorous head movements. But it would be
a self solving problem - if the batteries go flat,
the wearer will forever be turning their head to
point an ear at the speaker, thereby assisting the
recharging process. |
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Alternatively, a special recharging platform could
be sold with the hearing aid, on which the
behearingaided person would stand and be shaken
until the batteries were charged. |
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//I did have a thought about including an ear
trumpet. Then you could throw away the hearing
aid altogether.// |
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Ear trumpets are bulky and ugly, but I have a
solution for a sob-population of hearing-aid
wearers, namely those unfortunate souls who
have also lost an eye. Given that the eye socket
is now vacant real-estate in the head, an integral
ear-trumpet could be fashioned. I suspect that
the surgery needed to bring the distal end of the
trumpet into close proximity with the inner ear
would be relatively trivial. |
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