General Question

Ltryptophan's avatar

Is it possible to turn a normal object into a speaker at a far distance?

Asked by Ltryptophan (11073points) May 18th, 2010

Maybe you could shoot a laser at a piece of glass and it would act as a sort of speaker?

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13 Answers

andreaxjean's avatar

That sounds insane. What made you come up with this question?

Jeruba's avatar

I nominate a bathtub stood on end.

andreaxjean's avatar

@Jeruba A porcelain bathtub?

Nullo's avatar

Not a speaker, per se, but an elliptical or perhaps parabolic reflector might be what you’re looking for. Good for projecting sound across distance without disrupting ambient quiet.

Evan's avatar

I’m not sure that you’d be able to actually project sound with a laser, since a laser is basically a concentrated beam of light waves, not sound waves.

But I have heard that it’s possible to “hear” or “record” a sound being made at a distance by projecting a laser onto a surface (such as glass) and using the laser to record the vibrations being made against that glass by the sound waves.

Perhaps this is what you were thinking?

I suppose it might theoretically be possible to figure out some way of concentrating sound waves, in the same way that you can concentrate light waves to form a laser, and thereby cause sound vibrations on an object at a distance.. but i’m not sure whether that kind of technology really exists.

The only thing I can imagin is what @Nullo mentioned regarding certain types of surfaces that will reflect (and possibly amplify) some sounds that are directed at them.

anartist's avatar

The old-fashioned tin-can telephone that kids once used had a taut tied between the two cans to carry the vibrations. That would be needed. The bathtub on a mi8nimal level might catch some reflected sound like an echo but would miss most of it. Something large enough to create an echo—maybe—the only way you can go wireless.
But, for what you want, you need it hard-wired.

malcolm.knapp's avatar

The thing you need to do would be very hard because the only way to make a speaker is to physically move a surface, in this case the glass, back an forth. Laser light can not exert enough force on the glass to make it move. You could alway try with a bigger laser but you would probably melt the glass before you could get it to move.

If the important thing is to have a remote speaker you could use the laser to transmit the information to the speaker and then use that signal to control the driver that moves the glass.

One other note is that glass itself may not make a good speaker because it is so rigid. In the end you need a surface that can flex enough to create needed the pressure waves. If you want to turn a normal object into a speaker you could try a plastic plate or maybe a baking pan. I hope you get your idea to work.

IchtheosaurusRex's avatar

Yes, that’s possible. It even happens by accident. If you are sufficiently close to a strong AM radio station, all kinds of things will generate sound waves from radio waves by rectification. Early crystal radio sets could do this with entirely passive (no battery) circuits. A chain-link fence, or even dental work, can generate sound from AM radio under certain circumstances.

Surveillance equipment already uses a variant of what you describe to eavesdrop on people talking behind closed windows. A laser is shone on the window glass, and minute vibrations in the glass modulate the return beam, which allows the eavesdropper to hear what’s happening in the room from a considerable distance.

To reverse the process, you would need an infrared laser (glass is relatively opaque to IR in some wavelengths) of sufficient wattage to induce vibrations in the glass. You wouldn’t need much power to produce something faintly audible. If you wanted it loud enough to sound like someone was in the room speaking – much harder to do. One possible scheme is intermodulating a signal with the natural resonant frequency of the object you wanted to use.

jaytkay's avatar

Hypersonic sound kind of gives the result you want.

”...HyperSonic Sound, starts by generating ultrasonic — above the range of human hearing — sound waves, which can be focused in a tight beam rather than spreading out in all directions.

As these high-frequency sound waves pass through the air, they generate lower-frequency sounds that people can hear. By stepping into the “beam,” a person can hear sound that someone standing a foot or more away can’t detect.”

Sound-beam inventor takes the prize

Ltryptophan's avatar

@ChazMaz Thanks! GA, I hope everyone else will think so as well!

Ltryptophan's avatar

@ChazMaz from watching this video from TED, I immediately begin to see how valuable blind and deaf people will be for our future. I think it will become increasingly valuable to be able to tune out all the information they are going to start pumping at us. Not being able to hear may begin to be especially helpful if someone wants to go get something done without being harassed or just plain tricked out of progressing.

What a world! What a world! I’m melting!

Jeruba's avatar

@andreaxjean, yup. Preferably clawfoot.

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