Shotgun Speakers 101
September 6, 2006 10:34 AM   Subscribe

A friend of mine has told me about something called shotgun speakers and I'm fascinated. Basically, as her described them, they broadcast a sound in a very narrow beam so that only the target the speakers are pointed at will hear the sound. Is that true? How do they work? And more important, where can I get my hands on some? I'm a reality TV producer and I can think of dozens of applications. At least three of which may be ethical.
posted by rileyray3000 to Technology (20 answers total)
 
These guys seem to have what you are looking for, as do these ones.
posted by grimley at 10:37 AM on September 6, 2006


Sounds kind of like this, which is more of a weapon than a speaker.
posted by knave at 10:37 AM on September 6, 2006


Highly directional sound has been in use for a few years now in all sorts of advertising and point-of-purchase scenarios. Vending machines, for instance, which broadcast a pinpoint message, heard only by someone walking through a very limited circle.
posted by Thorzdad at 10:54 AM on September 6, 2006


it seems like joe pompei s the man to talk to you can find his homepage here actually as i look at it more in depth it just redirect to the link grimley provided. either way googiling joe pompei might yield more results, as i understand it he invented the technology.
posted by phil at 11:04 AM on September 6, 2006


If you really are a TV producer then you need to spend more time talking to your tech crew (sound, lighting, etc.), they should know all this stuff.
posted by Vindaloo at 11:35 AM on September 6, 2006 [1 favorite]


I'm going to point you to this article onDirectional Sound, and then unfortunately diverge onto a tangent.

One of the techniques for making directional sound is a parametric array. I have a friend who was in the acoustics department at Penn State who also worked at the Advanced Research Lab (ARL), which does contract research for the Defense Department. Anyway, they got a contract to research non-lethal weapons and decided to try using acoustics. They made parametric arrays that would play ultrasonic frequencies that would converge to produce audible sound only at a certain location. With an accurate enough array you could make a sound that was only audible to one person in a room full of people. They thought this was great, but then they had a brain storm.

They teamed up the parametric array with the Brown note and made a Poop Ray. Now not being a gullible person, I'm not sure whether or not this thing was real, but he said it was. Supposedly a prototype was made, and they could make a person in the middle of a room of people poop their pants. They could also make it into a ray that could be swept across a crowd causing near simultaneous loss of bowel control.

So, that's the derail. And a parametric array would produce the kind of effect you are looking for.
posted by jefeweiss at 12:21 PM on September 6, 2006 [1 favorite]


Google answers take...
posted by Roger Dodger at 12:41 PM on September 6, 2006


@jefeweiss,

I think your buddy was just pulling you're chain. The "brown note" urban legend persists but it's never been seen. It's hard to believe it could be real. The idea that some magic resonating frequency could be produced that would somehow cause all your bowl muscles to move in the exact manner to cause a bowel movement is more than a little ridiculous. Even more ridiculous is that idea that ultrasonic frequency sound could even get low enough to produce said brown note.
posted by crypticgeek at 1:36 PM on September 6, 2006


Even more ridiculous is that idea that ultrasonic frequency sound could even get low enough to produce said brown note.

Indeed, it can't by definition. The alleged brown note would be infrasonic.
posted by ludwig_van at 2:05 PM on September 6, 2006


Myth busters busted the brown note a couple seasons back...
posted by crewshell at 3:29 PM on September 6, 2006


Why would they be called "shotgun" speakers? Shotgun suggests something that is spread out, like a shotgun start in a golf tournament, or a shotgun offense in US football.
posted by langedon at 3:49 PM on September 6, 2006


Mythbusters is an entertaining show that may or may not provide any useful proof of anything, depending on the question and the execution. Their failure to find positive proof of a phenomenon isn't exactly scientific canon.

The brown note, as portrayed as some intestinal silver bullet, is likely a myth—the notion of a sound that makes you promptly crap your pants lacks nuance—but the effect of high-amplitude low-frequency sound is (if dim recollection is correct) documented as physically unpleasant. The myth of the Brown Note has roots in genuine acoustic research.
posted by cortex at 3:54 PM on September 6, 2006


Why would they be called "shotgun" speakers?

Shotgun microphones are used for targeted audio recording—they have narrow acceptance angles and so can be used to "target" audio, something that is particularly useful for things like dramatic filming.

The name "shotgun speakers" may be an analogue to that.
posted by cortex at 3:57 PM on September 6, 2006


Yeah, counterintuitive, I agree. I think the naming convention stems from "shotgun microphones," which are highly directional. The wiki link to the microphone article is here; you'll have to scroll down to read the following:

"Shotgun microphones are the most highly directional. They have small lobes of sensitivity to the left, right, and rear but are significantly more sensitive to the front. This results from placing the element inside a tube with slots cut along the side; wave-cancellation eliminates most of the off-axis noise. Shotgun microphones are commonly used on TV and film sets, and for location recording of wildlife."
posted by ZakDaddy at 3:58 PM on September 6, 2006


Drat you, cortex. Drat you to heck.
posted by ZakDaddy at 3:59 PM on September 6, 2006


Why would they be called "shotgun" speakers? Shotgun suggests something that is spread out, like a shotgun start in a golf tournament, or a shotgun offense in US football.

A "shotgun microphone" is a directional microphone that has a very narrow range of pick-up, that earned its nickname because it looks kind of like the barrel of a shotgun. This is basically the reverse of what a shotgun speaker would do.
posted by MrZero at 4:00 PM on September 6, 2006


Drat you, cortex and ZakDaddy. Drat you both to heck.
posted by MrZero at 4:01 PM on September 6, 2006 [1 favorite]


Can I be dratted? To heck even?
posted by oxford blue at 7:48 PM on September 6, 2006


I have a big problems with the way Mythbusters does things. It's pop science, and they often act like they conclusively prove things one way or the other when they don't. They say that they prooved that the brown note didn't exist, but they didn't. It's a negative proof, and they can't really say that they prooved that it can't happen. All they can say is that they didn't make it happen under the conditions they used.

I have my doubts about whether or not the brown note exists, but the Mythbusters didn't really add much to the debate one way or another.

And to answer the people who say that ultrasonic sounds can't make the brown noise, which is infrasonic, as I explain in my post, the parametric array causes audible sounds to be made from ultrasonic sounds by the principles of interference. They send out multiple simultaneous ultrasonic signals that add and subtract to make an audible (or subaudible) signal at a given location. This is definitely possible, and has been demonstrated.
posted by jefeweiss at 8:38 AM on September 7, 2006


Actually I'm NOT looking for the Brown Note. What I'm looking for is a way to project whispers to specific people at a distance that can only be heard within a tight area.
posted by rileyray3000 at 6:20 PM on September 8, 2006


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