Sound cancellation technology?

Apr 06, 2005 50 Replies

Low rumbling is an excellent candidate for active cancellation. But you won't be able to cancel the high-pitched metal rubbing past metal squeals, so it is probably not worth bothering about.

Basically active cancellation works well for long wavelengths and poorly for short wavelengths, where long and short are relative to the size of the area over which you wish to cancel the noise. Which is why cancellation with headphones is better, more frequencies have long wavelengths compared to the volume enclosed by the headphones -- and -- as someone else already pointed out, the high frequency crud can be blocked by the headphones.

You are more likely to succeed in buying the company operating the dumpster pickup and rescheduling their services than to block/cancel such noises.

Sorry.

Unless you shoot your ears out of a gun and doppler the noise to ultrasound ;->

Now why didn't I think of that? :)

I used to know someone who worked for Nelson Mufflers. In addition to making normal mufflers, they were also getting into sound cancellation. I had the impression from him that it ws doable, but expensive and that you could make it as quiet as you wanted, but that the weight and price went up as you demended more quiet.

In your case, where you just need the cancellation at the head of your bed (a single person?) that might not be too hard/expensive.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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Actually, both have been done: add and remove.

What, no smells? Geez, that's me out unless I change my diet! (Where's the fun in life these days??)

Ken

With all due respect to the my esteemed colleague, I know of no evidence of anyone removing reverberation or echos using active cancellation. It may be that there is a technology that I am unaware of, but I rather suspect that no such technology exists.

You can design a directional speaker system that puts less energy into the reverberant field, or use a filter to put less energy into frequencies that reverberate especially well in a particular room. You can even amplify early reflections and thus mask some of the reverberation. What you cannot do is remove reverberation with any sort of active cancellation. Once energy is put into the reverberant field it can only be passively absorbed.

Guy Macon

I should add that I believe it is also true that it is easier/cheaper at lower frequencies (longer wavelengths.)

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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Use a good audio amplifier and a good microphone, build an electronic circuit that should be between the pré-amplifier and the amplifier. This circuit should invert the entrance sign in 180 degrees. That is used in electrocardiogram to eliminate it collapsed of 60 Hzs / 50 Hzs.

"Luhan M> > How far has sound cancellation technology come, for use in a room area?

For

outside

Content-Transfer-Encoding: 8Bit

Fernando wrote:

Which part of the dozen posts explaining in detaial why this won't work are you having trouble unsterstanding?

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