Implementing Active Noise Cancellation

Thread Starter

ztjust

Joined Apr 1, 2012
12
Hello, so I have this tool which is very loud and I want to be able to make a ANC device in order to quiet it a bit for myself when I'm using it. So I'm trying to take the technology featured in headphones and some cars and implement it into a tool. So I'm trying to find a speaker size that would effectively cancel a lot of the noise. What would be a good idea for that?

Also, how much power or voltage would a thing like this take up? I want it to be as low power as possible.

An idea I had was to record the frequencies of the tool at operation, and then set the antinoise so I wouldn't need a microphone to take inputs. I think this would be a good way to reduce size and power consumption.

Thanks for any help.
 

wayneh

Joined Sep 9, 2010
16,125
Can you use a wall-wart, or do you need battery power?

You need microphones because the "anti-noise" must be timed to be out of phase with the noise. Otherwise it will just add more noise.

You know, a combination of noise abatement and hearing protection could be a much better overall strategy. In-hear "canal" earphones knock down ambient noise more than most active solutions. I used to wear them on long flights to Europe or Asia, whether I ran my iPod or not.
 

Thread Starter

ztjust

Joined Apr 1, 2012
12
Yeah I know I can just wear some ear protection, but I thought I would have some fun with this. And yeah, I would prefer battery power, something cordless.
 

wayneh

Joined Sep 9, 2010
16,125
And you want to build (rather than buy) just for the fun of it? I mean, Bose are expensive but there are some pretty inexpensive alternatives.

The folks here that might help you need to understand your motivations and goals.
 

dataman19

Joined Dec 26, 2009
135
Any "effective" anti-noise will probably require a sampling microphone.
There are very few that will just have an audio input. At least very few that will effectively dampen the noise...
You are looking at phasing a sound wave that is a "mirror" of the target offending sound. To do so you need to sample at a given distance, then calculate to effectively create a 180 phase sound at that point. If you design correctly and put the sound sampler at the noise source, then a simple 180 degree phased audio will suffice. But all sound amps are not alike,there are minute differences, and those differences could create issues with the viability and ability to effectively mask the offending sound.
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Then there are room acoustics. The sound from the offending source, and the sound waves from the speaker will bounce off walls at slightly different angles, and therefore reflected sound waves will literally be all over the map. The reflected sound waves may not be effectively cancelled, and could present as over whelming sound waves, bringing a whole new set of problems into the equation.
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It's not usually as easy to do this indoors (because of sound ambience) but can be done outdoors with less difficulty. Still, sound can bounce off nearby buildings (effectively making what seems as a whisper have an overwhelming echo.
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I am going to watch "this thread" with great interest.
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Oh yea - Good luck too...
...
Dave
Phoenix, AZ
 
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