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Piezo Wall Paper for Force Balance Noise Cancellation

Rooms or houses in neighborhoods located near practice aircraft carrier runways contend with after burner jet noise. While new building codes require builders to use passive sound proofing materials it would be better to have an active system that turns on when the outside noise exceeds a limit and/or at the flip of a switch.

Piezo would allow for much lower voltages than capacitors.

Sandwich piezo electric material between the 2 outer most layers of a panel. If this doesn't provide enough power to drive the piezo material in the 2 innermost panels in the reverse direction -- same expansion or contraction -- then the output of the outer panel may be amplified to whatever level is necessary to hold the innermost panel still.

It may be more effective to break the panel into a lot of independent areas. Three or more layers may be more cheaper and/or more effective than just 2.

Bret Cahill

Reply to
Bret Cahill
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No it wouldn't. Plus, it wouldn't work very well at all.

Reply to
HardySpicer

I don't know about that! You may have noticed that piezo speakers are always tweeters. That's because high frequencies don't require much volume displacement. If you try to generate low frequencies, you'll run into displacement problems with the "thin film" piezo material.

Industrial piezo drivers that I have seen are ceramic tubes, driven via a voltage on each end so the tube expands longitudinally. They require hundreds of volts to get millimeters of displacement.

In general, you can generate loud low-frequency sound via lots of small low-displacement drivers moving in phase. But for this application, each driver has to be able to cancel the unwanted sound impinging on it, and it alone. It can't rely on contributions from it neighbors, since they will have the same needs.

Best regards,

Bob Masta DAQARTA v6.02 Data AcQuisition And Real-Time Analysis

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Scope, Spectrum, Spectrogram, Sound Level Meter Frequency Counter, FREE Signal Generator Pitch Track, Pitch-to-MIDI Science with your sound card!

Reply to
Bob Masta

Enough layers ought to get the required displacement.

Without the numbers to compare piezo to caps it's hard to say but 500 V sounds better than 5 kV.

Was that for a speaker? As you mentioned on the cap thread just holding something still doesn't require linearity.

There are all kinds of piezo materials. We need the one that,

  1. has the highest expansion-contraction / voltage coefficient, and,
  2. costs the same as gypsum board.

Producing multiple layers might not be all that more expensive than just 2 or 3 layers.

One advantage to the piezo panel is, if necessary, it could be printed like any MEMs device to have tens of thousands of independent "mics" and negative speakers at a tiny fraction of the cost of other systems.

They produce 12 mega pixel cameras for $40 so this ought to be duck soup.

The outer layer(s) receiving the noise would be wired in parallel to all the subsequent layers, probably with amplification.

I've wandered away from a servo solution but it's hard to ignore the fact that the mechanical energy in the noise was won at a very high price. The re heat cycle is horrifingly inefficient. If it is so difficult to keep the high quality energy from turning into heat _before_ it becomes sound, how come it so difficult to turn it into heat _after_ it becomes sound?

It doesn't seem fair.

Reply to
Bret Cahill

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