Noise cancelation ?

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Davebones

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Has anyone been involved in noise cancelation projects ? When I worked in power plants they installed some systems around some of the large motors . We have some manufacturing floor areas that get pretty loud . Just looking to get some information on what's out there now ...
 
Davebones said:
Has anyone been involved in noise cancelation projects ? When I worked in power plants they installed some systems around some of the large motors . We have some manufacturing floor areas that get pretty loud . Just looking to get some information on what's out there now ...
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Large motors just do make a lot of noise. A lot of paper mills we went to were typically had around 15 motors some of them 30kW up 500kW. Silencing them is not a practical option. We all used quality ear defenders when we went into the mill area.
 
Davebones said:
Has anyone been involved in noise cancelation projects ? When I worked in power plants they installed some systems around some of the large motors . We have some manufacturing floor areas that get pretty loud . Just looking to get some information on what's out there now ...
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Industrial hydraulics systems approach it primarily 3 ways, We ATTEMPT to design for less noise via construction methods, flexible joints and mounts, pumps inside reservoirs, lower speeds. We enclose, often in rooms, occasionally in absorbing enclosures. We use quieter motors and pumps; there are relatively costly extremes here with fluid flow through motors; they can be made smaller and quieter and are LESS efficient,
 
One of our customers used to get specs that would call out maximum decibel ratings of certain kinds of equipment, usually at certain distances from the equipment. Often standard equipment just couldn't meet these requirements and they would need to add isolating pads, flexible connections in the piping, and often some kind of walls to reflect the sound upward. Sometimes they had some kind of sound reduction insulation even. Just depended on what level of sound reduction was needed to meet the spec. A lot of times it didn't take very much. Other times it got pretty elaborate.

One of the customers I work for regularly installed a giant door across part of a building. This was done solely to reduce the sound level in part of the building. The door is like 30 ft high and several hundred ft long and lowers from the ceiling to allow the crane to pass through. When they are done moving stuff they close the door and it is supposed to keep sound transmission down from the other end of the building where there is a lot of noise.

In the noisy end of the building One is supposed to wear both earplugs and muffs due to the potential sound pressure. The other end of the building on the other side of the door requires only plugs or muffs but not both. Personally I can't tell any real difference from one side of the door to the other.
 
None of the posts so far address anything about noise cancellation, only abatement.
Back in the 90s, the company I worked for did an R&D project on active noise cancellation. The idea is that you input the noise to an amplifier, shift the phase so the extent that you can project soundwaves exactly 180 degrees out of phase with the source such that they cancel out. I wasn’t involved with the project, but after much time and money expended,it was abandoned.
 
retirede said:
None of the posts so far address anything about noise cancellation, only abatement.
Back in the 90s, the company I worked for did an R&D project on active noise cancellation. The idea is that you input the noise to an amplifier, shift the phase so the extent that you can project soundwaves exactly 180 degrees out of phase with the source such that they cancel out. I wasn’t involved with the project, but after much time and money expended,it was abandoned.
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Noise cancellation can be very useful for low frequencies from large equipment and also for higher frequencies from smaller equipment. The closer a noise generator is to a point, line, or wall source, the easier it is to position speakers or other tranducer to (partially) cancel noise at a distance. For a large and irregular shaped source, it is hard to match its directionality in the cancelling sound.
 
GoldDigger said:
Noise cancellation can be very useful for low frequencies from large equipment and also for higher frequencies from smaller equipment. The closer a noise generator is to a point, line, or wall source, the easier it is to position speakers or other tranducer to (partially) cancel noise at a distance. For a large and irregular shaped source, it is hard to match its directionality in the cancelling sound.
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Yes, large and irregular things. I think the greatest noise I encountered was an arc furnace. Very large and very noisy. Noise cancellation was not an option.
 
GoldDigger said:
Noise cancellation can be very useful for low frequencies from large equipment and also for higher frequencies from smaller equipment. The closer a noise generator is to a point, line, or wall source, the easier it is to position speakers or other tranducer to (partially) cancel noise at a distance. For a large and irregular shaped source, it is hard to match its directionality in the cancelling sound.
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These were large blowers with steady, low frequency noise. There was some success in the lab, but commercializing the technology to account for all of the installation variables possibly encountered in the field was overwhelming.
 
Noise cancellation works best at the point of observation, i.e., the ears. If the point of origin of the noise and that of the cancelling waveform are not the same, there will be differences in relative phase that change with respect to point of observation that get more pronounced the higher the frequency and the farther apart the sources are. Phasing of noise source and cancelling waveform need to be precisely inverted from each other at the point of observation for it to work, and it's possible that at some points of observation the waveforms will constructively rather than destructively reinforce, so the noise level will be higher rather than lower.
 
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I was in a room with some huge compressors and the company had bought an active noise cancellation system. I barely noticed the difference. Even with the noise cancellation on, I still needed hearing protection. So what was the point?
 
retirede said:
None of the posts so far address anything about noise cancellation, only abatement.
Back in the 90s, the company I worked for did an R&D project on active noise cancellation. The idea is that you input the noise to an amplifier, shift the phase so the extent that you can project soundwaves exactly 180 degrees out of phase with the source such that they cancel out. I wasn’t involved with the project, but after much time and money expended,it was abandoned.
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The hard part is doing noise canceling over a large area. If there’s only a couple of places people would be then you could work something up, but if it’s a wider area or you’re dealing with higher frequencies it would be impractical to try to implement noise canceling. It would be significantly cheaper to supply noise canceling headphones for the workers.


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A.Adams said:
The hard part is doing noise canceling over a large area. If there’s only a couple of places people would be then you could work something up, but if it’s a wider area or you’re dealing with higher frequencies it would be impractical to try to implement noise canceling. It would be significantly cheaper to supply noise canceling headphones for the workers.
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Impractical to try and impossible to do, IMO.
 
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