Active Noise Control (ANC) for construction equipment?

[claudiodeviaje]

Hello Everyone!

As some of you might know, in 2006, according to noise norm for 2006 for construction equipment, the noise produced has to be strongly reduced (at least here in Europe, I don't know in the US).

We are trying to reduce the noise levels of our machines (excavators, notor graders and wheel loaders) by using standard passive noise cancelation. Roughly seen, we are covering everything with foam! I've been reading about Active Noise Cancelation and how good it can be.

I've found in the Internet, just prototipes for Active Noise Control for mufflers, air intakes and for radiators (for fans) but no commercial units.

Could someone point me to copmanies who build this kind of equipment commercially?

Thank you for your help.

Claudiodeviaje

 

[GregLocock]

Sadly there aren't any bolt-on systems. You could try Lord in the USA.

I don't think you'll have much luck to be honest. A conventional passive system will probably be more effective.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[EricZhao]

Active noise control tech is still in the academy research phase. Personally, I don't believe it is a promising tech.

 

[MikeHalloran]

ANC has a chance of working, >for the occupants< of a closed vehicle.

I get the impression that you're trying to reduce drive-by noise, which would require some sort of phased negative acoustic radiator for each noise source on the vehicle.

It would have a chance of working on the exhaust pipe, except for heat and corrosion issues, but passive technology exists for dealing with that already; it just takes up a lot of volume. Figure on a muffler with roughly the same gross volume as the engine itself. {Overall envelope volume, not cylinder displacement)

Actively offsetting the noise emission from cooling fans, gearboxes, and valve clatter, for external observers from arbitrary directions, is ... I don't want to say impossible, but I'll say challenging in extremis.

Look at alternating layers of foam and mass- loaded plastic, applied to the radiating surfaces.





Mike Halloran
Pembroke Pines, FL, USA

 

[vanstoja]

As the preceding inputs and your own search on the web suggest, Active Noise Control (ANC) for mechanical equipment is still in the developmental stage and its application may be a difficult undertaking at this stage. From my experience, the most advanced techniques involve ducting fluidborne noise suppression with a company called Nelson, I believe, from the US midwest being one of the early leaders and structural panel vibration suppression using piezoelectric "patches" attached to the panel surfaces at predetermined locations established by performing modal analysis of the structure to determine airborne radiated noise transmission hotspots. Papers on piezoelectric ANC technology have appeared in the ASME J.Vibration and Acoustics among other sources. I don't know what companies are involved in piezoelectric patch production.

 

[Tmoose]

Works well in a lengthy duct or pipe with frequecies whose wavelengths are > duct width diameter

Digisonix designed and built some commercial systems for use in HVAC ducts and stacks. Pretty impressive. "turn off the noise" or maybe "turn on the silence."
Now they are part of someone else and are reportedly working on engine (exhaust/intake ?) noise.

http://www.signalsystemscorp.com/anc_news.htm

 

[Rob45]

"Active noise" has been made to work rather well by a couple U.S. companies, when applied primarily to sources rather than to receivers, but it has some severe limitations.
Due to cancellation error, it is limited to rather low frequencies, and due mostly to processor (and algorithm) limitations, it is also limited to machinery that does not change speed very quickly.

I have seen active noise technology applied very effectively, however, to intake noise on constant speed equipment such as blower-type bulk transfer machines, and to industrial vacuums - floor sweepers.

Regarding piezo-electric "patches" for active vibration control: "Vibration-X" is in that business, in Winchester, Mass. They have both active and passive piezo-devices for vibration control.

But I think you need to go back to basics and understand all your noise sources, and treat them individually, rather than just trying to put a big foam "band-aid" over the whole machine.