August 19, 2004

2:49 PM

My recent experience at work has led me to wonder whether there is any sort of personal noise cancellation gun? I envision a device or appliance that you can point at someone obnoxious to negate them using noise cancellation technology.
posted by mert to (10 comments total)

The best you could hope for would be some "pink noise" headphones (mentioned in a previous thread). Using directional sound to mute the entire acoustics of a room require an exact sequence of matching harmonics.
You'd need an array of guns (a battery of neutralisers) which could shift pitch in real-time to drown out the chatter, in addition to the office machines, etc.
posted by Smart Dalek at 3:00 PM on August 19, 2004

Noise cancellation only works for steady, predictable tones. Engine noise, fan noise, yes. Chattering co-workers, no.
posted by ook at 3:38 PM on August 19, 2004

Doesn't noise cancellation technology work by adding "two [sound] waves together ... and if those waves are completely out of phase ... [they] cancel each other out."?

So why not try broadcasting something completely out of phase with normal conversation -- opinionated talk radio, for example -- to cancel it out?

You'd have to determine which "normal" you were cancelling out and broadcast the appropriate opposite back at it. This may have the added effect of driving the chatterer screaming from the room, which would be OK too.
posted by mmahaffie at 4:47 PM on August 19, 2004

I have a small metal device that emits a single, fairly loud sound when I use it, but if it is properly aimed at someone obnoxious, it is very effective at silencing further annoying sounds coming from that person.
posted by spacewrench at 5:10 PM on August 19, 2004

Nice, spacewrench, but perhaps not inducive to one's long-term freedom.

Inducive? I'm not even sure that's a word. I'm really, really tired.
posted by five fresh fish at 6:56 PM on August 19, 2004

I'd like to see better broadcast-format active noise cancellation technology.

They'd be just the thing for the perimeter of a night club or illicit dance party.

Not to mention, cones of silence and that sort of thing.

Though, I wonder how potentially harmful high-amplitude audio interference peaks are? Would it produce weird ultra/infrasonics?
posted by loquacious at 7:36 PM on August 19, 2004

white noise works buy sticking the inverse waveform on top of the originating. It works fine on point sound systems such as an engine (which doesn't move) or earphone (which are bolted to your head). blocking out a moving target without headphone could be more interesting. The pink noise option is probably the best one.
posted by twine42 at 4:01 AM on August 20, 2004

I do appologise, ladies and gents. It looks like I lost the ability to type English. Ahem...

The system mmahaffie mentions is white noise. It works by taking the original waveform, inverting it and playing it back so that the two superimpose and cancel each other out. This rarely works perfectly (because of the electronics lag) and tends to result in a characteristic buzzing tone.

As ook mentions, this would work much better on something predictable (because you can be proactive rather than reactive) but this doesn't make it worthless.

These systems work pretty well with a known sound source or target. Engines can be cancelled because they are small origin points and you can attach the speakers to the system. Any system using headphones is great, because you can intercept the sound, flip it, and cancel it out inside the ear. since the original sound also gets muffled by the headphone arrangement, I assume that the cancellation drone is less noticeable.

A few years ago there was talk of a sound system that they were considering for cinemas. The theory was that speakers broadcast an ultra or infra (I forget which) sonic sound wave that was directional. Where two sound waves overlapped, they caused a burst of audible sound. The theory was that you could make a helicopter move around the cinema by playing with this effect.

Theoretically, if you could target the person, record their voice, flip it and then use this technique to stick a white noise source a few inches above their head, then you could cancel them out.

Unfortunately, I would guess that the delays in getting the sound and then bouncing it back in this way would either fail to work or would turn the person into a dull drone - roughly what you were originally trying to cancel out to start with.
posted by twine42 at 4:24 AM on August 20, 2004

Bring a TV remote to work. When the droning starts, point the remote at the droner and conspicuously press the mute button, looking at the remote in consternation when it doesn't work.

If social engineering doesn't work, nothing will.
posted by stonerose at 5:57 AM on August 20, 2004

The system mmahaffie mentions is white noise. It works by taking the original waveform, inverting it and playing it back so that the two superimpose and cancel each other out

Nitpick: good explanation, wrong terminology. White noise is just constant random noise, like the static noise you can no longer get from your TV.

Which reminds me of a story: my wife was teaching a writing workshop, and they were discussing the first line of Neuromancer: "The sky above the port was the color of television, tuned to a dead channel," and how that sets the gloomy mood for the book -- but one of the participants insisted she thought it was a cheery, happy image that didn't fit at all. Took everyone a while to figure out that she had never seen actual TV static, and was thinking of the bright blue screen that modern televisions use to block it out. Kids these days. I tell ya.
posted by ook at 8:38 AM on August 20, 2004