Sound cancellation technology?

"Guy Macon" wrote in message news: snipped-for-privacy@corp.supernews.com...

That response almost came from here before I realized such cancellation was not literally impossible. Imagine that every surface of the room where sound might enter is covered with small transducers able to sense and produce sound. Imagine them processed and driven so as to cancel what would otherwise have been transmitted sound. Viable? Surely not for home use, today. Could something like that be done today? Maybe, if it really mattered enough. In some future world? For that, talk to anybody who was around in the early 1900's about what they see today.

Yep, and they still wont see consumer cars that fly. Its the things that are not predicted that tend to happen - the $99 home VCR, one dollar computer chips, and actors winning politcal office.

You have to have the right shoe ;-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

How far has sound cancellation technology come, for use in a room area? For example, for a bedroom?

I need some sound cancellation in the bedroom due to street noises outside while I'm trying to sleep.

I know they have it inside closed headsets for pilots etc, but is the technology viable yet for a closed room sized area like a bedroom?

Ok, but think about it, what else gets through the closed windows and doors, except lower frequencies?

When they schedule an early morning dumpster pickup across the street from me, even my white noise generator won't stop that low rumbling garbage truck sound.

Swell. I'll cement up the windows and put lead sheeting all around the room. Not.

What was that comedy years ago, where they had the "cone of silence"? :)

Not only is it not viable, it never will be viable. You can't cancel a sound wave unless the cancellation source is a small fraction of a wavelength away from your ear - which means that you cant cancel anything above 50-100 Hz in your bedroom.

White noise can mask the outside noise. Running a room fan is a good way to do that.

Heavy curtains can help if it's mostly coming through a window. Weatherstripping and double-pane glass might help as well.

It isn't very expensive to add blown-in insulation to a wall.

An interesting bit of trivia: if you want the greatest amount of sound blocking with the minimum weight, lead sheeting blocks more sound per once that anything else. Impedance mismatching...

There are windows you can buy with a film inside that muffle sound or you can create your own 'storm' window with heat insulation film, a frame and another layer of glass or polycarbonate. Ear plugs are another posibility? Not electronics but then, they work.

Voice of freedom wrote:

Voice of freedom wrote:

Systems have been built in large halls to get rid of un-wanted echos as well as enhance the on-stage performance. I understand that some of these systems are dynamic, so that sounds from one part of the stage are processed differently than others. That said, it would seem to be very possible to achieve at least reasonably acceptable results. If you do not mind experimenting, you might see if you can get a surplus headset that has the cancelling technology, along with as much technical info as possible. One or two microphones placed outside - say one mounted on cushions so that it only picks up sounds in the air, and the other mounted near the base of the wall nearest to the traffic so that it pickups sounds by "conduction" from the wall (and not by air). These mikes are the "reference" noise pickups; the waveforms would be processed before feeding to speakers inside the house/bedroom. Mostly the lower frequencies are the culprit, so some of the processing would appear to be possible via filtering. The basic idea is that the sounds from the indoor speakers are "EQ" in both amplitude and phase across the spectrum of interest - to cancel the sound that is transmitted via air thru windows and walls, and cancel sound conducted via wall and earth movements (truck rolls by). The "air" reference is processed for the first part, and the "conducted" reference is processed for the second part.

I use the word "processed" on purpose, as a DSP might be necessary to achieve optimum results. The surplus noise cancelling headphones may or may not have a DSP, depending on how new it is; one would try using two - one for each of the "channels" i mentioned.

If you have some kind of network with contacts to sound engineers in opera houses, sound stages, etc, do not hesitate to ask if any "exotic" technology is used; and for help.

The limitations are not in the technology. It is just a physics thing

- you can't cancel sound in volumes larger than a fairly small fraction of a wavelength.

Not now, not ever.

Pearce Consulting

For

Simpler, more effective, and most importantly, currently available:

I use earplugs with great succes..

I sold and installed the Headsets, Inc. Active Noise Reduction (ANR) kits to pilots for a while back in the mid nineties. Kept up with the advances back then. If I recall correctly, Bose Laboratories in Boston was experimenting with "whole aircraft cabin" ANR systems, and that some Business Aircraft manufacturers were offering Bose's ANR option to anyone who could afford it. The option was expensive, requiring a number of well placed speakers, a fair amount of electronics, and extracting some useful load. For reference, refer to indices of the SAE publication "Aerospace" from the mid to late nineties. I think I also recall that someone was building similar ANR systems for OTR Trucks.

Recollections aside, in my opinion, ANR equipped headsets were, and are a real plus while flying in general aviation aircraft. Most systems I tried cancelled much of the lower frequency engine and exhaust noise, and certain components of slipstream noise. The design and shell of the headset earcups knock down much of the higher frequency components. All of which makes for a more relaxing, less tensing flight. A bedroom sized system might work similarly well for lower frequencies, but I doubt there would be much protection from higher frequency components such as sirens, plant whistles, and the like. Just like the earcup shells on a headset, one would probably need to super-insulate the walls of the bedroom. One problem which was dominant with all systems was a "hiss", almost like "white noise". This could be a bigger problem on a room or cabin sized ANR system.

Hope that helps to answer the original question. Aloha, Dave

Even the Chief of 'Control' knew that would never work. :-) (Remember Laraby tapping the Cone to get their attention once? :-)

On the original problem, if some noise-canceling earmuffs aren't going to be useful (and I assume they wouldn't be), then about the only option you have (if it's your house) is to double-glaze and get some in-wall insulation, probably an extra soundproof layer of wall boarding (we call it gib - no idea what you'd call it), and something under the floor. There's a myriad of soundproofing materials available so a search would reveal them. However I suspect you aren't into a huge mechanical solution. I sympathize with you, but can't think of any other way out.

Cheers.

Ken

Your name is Rube Goldberg?

Yes, I've heard that some experimenters have come pretty close to being able to do very simple sound cancellation in a room area, without headphones, but not close enought to produce a perfect product to sell. High speed DSP was mentioned.

outside

I already have double windows, which helps some, but the place across the street is running some kind of home shop business and fills up their dumpsters a couple of times a week, then calls for pickups. The garbage truck is a big diesel rumbling thing and that wakes me up, right through the walls etc.

"Dave Fase" writes: ....

....

One quick question, having tried three brands of noise cancelling headsets, all three seem to do a good job at reducing low frequency noise like the roar and rumble inside city busses, engine noise, etc. But that just brings out the conversations that would otherwise be buried by the roar.

Strictly dealing with headsets for this question, is not also cancelling voice/music by design, by limitations of physics, by limitations of processing power, by limitations of battery power or by cost of components?

On related notes, but not wanting to derail answers to my question, perhaps a decade ago I was sitting in a class where the prof claimed that he had direct knowledge that the Cadillac NorthStar was named NorthStar because N S recognized that they had built Noise Suppression and noise cancellation into this car line. I was interested in this and contacted Cadillac about this at the time. They responded that this was not the case. We never could resolve this contradiction.

Since that time we have seen advertisements by the companies selling trucks to the public, describing how much work they put into making the sound of their trucks make it clear that the owner has really really large male equipment.

Please, I'd like some refferences on that. The tests I've conducted (two