What is Noise Cancellation?

define

Noise cancellation technology is a growing field that capitalizes on the combination of disparate technological advancements. The purpose of the technology is to cancel or at least minimize unwanted sounds. Modern lives seem full of all sorts of noise, some of which are dangerous to our ears. In fact, many people, especially those who live and work in cities, have very little quiet time during the day.

Noise cancellation technology aims to remedy the excess noise that we experience. Of course there already are low-tech solutions to the problem. Ear-plugs and sound dampeners are available, but they are not very convenient nor very efficient. Noise cancellation tries to 'block' the sound at the source instead of trying to prevent the sounds from entering our ear canals.

But how does it work? Sounds travel through the air or through liquids in the form of waves, and each of those waves has a particular shape. Noise canceling technologies first rely on small microphones that detect the sounds in a given environment. A digital signal processor determines what sound wave is required to cancel the unwanted sound wave and then it creates that sound and amplifies it through speakers or headphones. One way to understand this is to imagine a 'positive' sound and a 'negative' sound created at virtually the same time, and these two sounds cancel themselves out thereby bringing the listener closer to silence.

These technologies are in their early stages, and they cannot completely omit sounds, but improvements are consistently being introduced. The hope is that one day that these technologies can be used to minimize all sorts of unwanted sounds around us. Imagine, for example, a lawn mower, hair dryer or vacuum cleaner that included a noise canceling system, thereby greatly reducing the unpleasantly loud sounds.

Noise canceling headphones are already available. The headphones cancel out unwanted ambient sounds allowing the listener to focus solely on the music. The latest versions of these noise canceling headphones work surprisingly well, and new applications are certainly on the horizon.

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12
In this part of the world, hurn speakers are used by Mosques at anytime and anywhere without consedering other people that are not sharing their view. Please, we need this system to have peace in Africa -- especially in Nigeria.
- anon49671
10
Are there noise cancellation systems that work where a dating or married couple is sharing intimacy in a house with children? The application, of course, would be planned so that *absolutely* no sounds would emanate from the bedroom! I suspect there would be widespread interest in such an application of the technology.
- anon33918
9
We would love to find out about any systems which would help counter noise outside..ie traffic...as would our neighbors.
- anon33792
7
No answers to the questions above, I see. I, too, am interested in a system that can help an entire neighborhood.

We have a brand new racetrack as a neighbor who's cars run everyday for 10 months of the year. Some of the spectator races include the Grand Am, ARCA, Mazda Formula X- so you can see they are some of the loudest things going in the racing circuit.

For folks living close (2 miles and closer) to the track, they are forced to sit inside with windows closed, the air conditioner on wonderful, on sunny gorgeous days when they really want to be outdoor in their once peaceful yards.

*Please*! Any answers to these questions, even if it's bad news. If something like this can be developed, then the racing industry as a whole would love it as they can then race all they want and not have lawsuits forcing them to close down. Lots of money to be made here if something like this can be implemented.

- pistolpost
6
Assume you are listening to music in a somewhat noisy environment using noise cancelling headphones to eliminate the outside sounds. Since the headphones are eliminating certain sounds which are truly frequencies, is not the music also being affected in those frequencies?

In an extreme case, if you fed the music to both a set of speakers and to a noise cancelling headset, the headset would cancel out the sound hitting them from the speakers and you would then hear nothing, unless you could overboost the volume only to the headset. Therefore any outside sound would diminish the pure music reproduction in those frequencies as heard through the noise cancelling headset. Discussion?

- ronjohnstone
5
Very interesting technology... Does anyone think it could be implemented in a room/pod?

Thanks

- anon11356
4
Surely if this is going to work at an individual house level, it is necessary to measure the 'incoming' noise profile at the house in question and produce the 'negative' anti-noise locally?

I would think the biggest problem here is to achieve this processing quickly enough and to project the ant-noise sound so that it has a broad 'sweet spot'.

- anon8964
3
Hi Jsweet, you might be on to something. Here are two additional thoughts...

* If the issue is an inheret delay, could we somehow tap into a harmonic opposite of a sound at a higher frequency

* Create a profile called train that has the basic sound of a train. Then install it at the desired locations. Even though it's not perfect cancellation it would certainly serve to dampen the sound.

I do have two counter arguments, especially if you you are looking for pure cancellation. The first is minor: If you record the sound of a train in one place it may not sound the same as it will further down the track. The net effect I assume would be a dampening effect, and I think that would be effective.

The second, in terms of a train and to some degree traffic is more significant: A train, and highway traffic for that matter create a significant amount of seismic noise that in turns vibrates nearby structures and causes new sounds.

In business terms this criticism might serve you well because you can sell a better solution customized for every house than you can sell in a one size fits all solution. You can also sell ongoing support for keeping the quality of dampening consisitant as sound conditions change.

Larry Boeldt

- anon5869
2
It occurred to me that noise cancellation technology relies on the ability to generate a complimentary signal where its output would be 180 degrees out of phase with the incoming signal. Virtually impossible in a single unit due to the delays inherent in the circuitry. Would it be possible to design a system which would pick up the sound (a train), transmit it to a receiver some distance away, and have that receiver overlay the complimentary signals in real time to cancel the noise at the end. I see this as a way to silence unwanted noise for entire neighborhoods. A main station which receives the sound, re-transmits the complimentary signal at a speed greater than the speed of sound, and each remote location (house, room, yard, etc...) has a receiver which syncs up the signals and generates the complimentary sound to cancel the noise. Is there a company doing this at this time? Shall I get a patent?!
- jsweet
1
Are any systems being developed which can help counter noise outdoors? And if so who by?
- anon2217

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