Definately not looking for headsets

[katka]

I am looking into creating a slim good-looking noise canceling devise that one could, let's say, place on the restraunt table and cancel out most of the background chatter by a resteraunt full of loud and hungry people making a meal out a much more enjoyable and intimate experiance. Is such a devise feesable? I am not looking for headphones or anything that you wear. More like something that could be carried in your purse, then taken out and turned on at will and the person sitting across from you at the table would get the same benifets. Any imput?

 

[KingNothing]

I don't want to rain on anyones parade, but that would be completely infeasible.

First of all, in order to cancel noise without putting up some sort of physical barrier, you'd need to use destructive interference. That said, you'd need all sorts of microphones set up in various directions to 'know' what sound is coming towards the table. You'd then need a hugely, hugely powerful computer to analyze the sound and where it comes from, and finally speakers to produce sound that interferes with the sound coming towards you. This last step is probably the most infeasible, if not completely impossible.

To take things a step further, even if you DID have all that, you'd still be sending out sound waves all over the room which would then bounce back and the whole process would repeat itself.

What do you mean by "looking into creating"? I hope you aren't seriously considering dedicating any time to this.

 

[dav2008]

Plus you would have to factor in the sound at each person's left and right ear, the location of which changes every second and somehow beam a sound specific to that person.

I'd say stick with the headphones :D

 

[chroot]

Finally, the noise-cancelling sounds made by your device would be heard as intolerable noise by everyone else in the restaurant.

- Warren

 

[russ_watters]

You'd then need a hugely, hugely powerful computer to analyze the sound and where it comes from, and finally speakers to produce sound that interferes with the sound coming towards you. This last step is probably the most infeasible, if not completely impossible.

"Possible", but utterly ineffective. A Bose headset cancels noise in the direction the sound is traveling. This device would need to cancel noise going in the opposite direction. That means that the noise to be canceled has already been heard by the people at the table, so only continuous sounds could be cancelled, and even then without much effectiveness.

 

[Moonbear]

I'm also wondering how it would distinguish between all the other noise in the restaurant, and the intimate conversation you were trying to have with your dinner companion.

 

[Pengwuino]

A professor at some university had done a project with some graduate students to cancel out the noise in a computer tower. Supposedly it was pretty good but they said it took a lot of computing power and it was very hard to actually cancel noise from multiple sources (let alone a room full of chatter, dishes, kitchen and in general, everything you hear in a restaurant)

 

[Cyrus]

-Active Noise Cancellation

Noise and vibration are annoying to passengers in helicopters and other aircraft. Traditional sound-absorbing materials can be very effective in reducing noise levels, but are too bulky and massive for application in aircraft. An elaborate approach is an electronic system that cancels noise. The diagram of such a system is shown in figure PA6.1. A microphone near the source of the noise, such as the engines, samples the noise before it enters the passenger area. The resulting electrical signal passes through a filter whose transfer function is contiunously adjusted by a special purpose computer to match the transfer function of the sound path. Finally, an inverted version of the signal is applied to loudspeakers. The sound waves from the speaker are out of phase with those from the noise source, resulting in partial cancellation. Another set of microphones on the headrest monitor the sound experienced by the passenger so that the computer can determine the filter adjustments needed to best cancel the noise. For more information, you may wish to read "Noise vibration and control" in the september 1994 issue of Aerospace Engineering. According to the acrticle, systems such as this, weighing 50 to 100lbs, achieve results comparable to that of up to 1000lbs of sound-absorbing materials.

Sources: "Anti-noise system," aerospace engineering, december 1993, pp.15-16, L.E. Trego, "Noice and vibration control", Aerospace engineering, sepetember 1994, pp.10.12.

In short, It can be done. In your case, its just not practical.

 

[russ_watters]

That's the same technology used in Bose hedsets, Cyrus, different from what katka is trying to do. And what took 50lb of computing power 10 years ago can now be done with a computer that fits in a pen.

edit: oops, similar, but not the same. Headphones are essentially 1-dimensional, so the computing power required is significantly smaller than in that type of system.

 

[Cyrus]

What I posted was not a headphone, it's a loudspeaker.

Edit: It's also not 50 lbs of computing power. It's 50 lbs of microphones, speakers, and computers. So you could have a smaller computer, yes, but I don't know if that would drasitcally change the overall weight.

so only continuous sounds could be cancelled, and even then without much effectiveness.

Replacing 1000lbs of sound material with 50-100lbs of electronics is a 10 fold reduction in weight. That is a significantly effective technology.