h a l f b a k e r yExpensive, difficult, slightly dangerous, not particularly effective... I'm on a roll.
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A small wind-turbine type of device is attached to a microphone, such that whoever speaks into the microphone will also generate some energy. The more they talk, the more energy is produced.
Energy would also be produced when the thing is just waved around, too, as is frequently done by most people
holding a microphone.
Obviously, every politician and news reporter and pop singer should have one! For starters....
Near-dc-processing for microphone signal
Near-dc-processing_...microphone_20signal
Semi-related [csea, Apr 07 2010]
The Microflown
http://www.microflown.com/
vector-based microphone [csea, Apr 13 2010]
Sound level vs. distance
http://www.sengpiel...ulator-distance.htm
A good write-up on acoustical terminology [csea, Apr 13 2010]
Getting baked....
http://news.discove...ersation-power.html
Probably not a turbine, of course. But the basic concept seems similar enough! [Vernon, Sep 15 2010]
[link]
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Wouldn't an internal turbine, placed somewhere in the throat, be exposed to a higher, more consistent source of air currents? |
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Yes. But that's not the point, here; I posted this because of the silliness factor. |
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There could possibly be enough energy extracted via this method or that in my similar idea [link] to provide self-power for a condensor microphone. |
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One might have to breathe heavily to get it started... |
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Perhaps. But is wind sound? All is vibration. Even weather / atmospheric pressure is vibration, albeit very low frequency. |
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Ever listened to speech with all the breaths edited out? It sounds very unnatural. |
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[BunsenHoneydew], the silliness factor here is that the turbine needs to be rather delicate, to catch the exahalation-of-breath associated with speech. There is indeed a very slight breeze that is part of the process of talking. |
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Which is why microphones have pop shields, or you stand further away from them, using the intervening air as your pop shield. |
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In short, if any wind energy is reaching the microphone, you have a useless signal. If you have a useable signal, you have no wind energy. |
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Have a look at the microflown [link]. It has dc-response up to 1.2m/s. Suitable adaptive FFT filtering should be able to separate wind from voice. |
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Or use a piezo microphone, which generates energy from the vibration of the speech itself. |
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Note that the quantity of energy is miniscule. Sound energy is subject to an inverse power law. The enrgy available to be harvested in a small area (microphone) at any distance from the source is so small I can't be bothered to calculate it. |
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The acoustic power available from human speech is fairly complex, but a predominant factor is inversely proportional to frequency, which is to say that there is significantly more energy at low frequencies, approaching dc (one directional airflow.) |
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A turbine located very close to the mouth should be able to isolate the near-dc component and collect a small amount of power. |
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"The acoustic power available from human speech is fairly complex, but a predominant factor is inversely proportional to frequency, which is to say that there is significantly more energy at low frequencies, approaching dc (one directional airflow.)" |
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Not true: For a given amplitutde, higher frequencies carry more energy. Imagine a single particle moving to and fro. Each oscillation requires accelerations of that particle. Do it twice as fast (i.e. double the frequency) and there are twice as many accelerations. Because each acceleration also has to be twice as large (to move the particle the same distance in half the time) sound energy is proportional to the square of the frequency. |
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[Twizz] What you say would be true if amplitude were constant. But amplitude (particle displacement) is an inverse function of frequency for a given SPL (sound pressure level.) |
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For instance, amplitude of a 60Hz tone at 100 dB SPL is about 12 microns. At 30 Hz, the displacement for the same SPL is 24 microns, at 15 Hz, 48 microns, etc. |
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