Active Noise Control / A challenge to get rid of noise.

I have a challenge for my freinds in the Grow-room, I bet you have wrestled with this very same problem. It would be nice if we could put our heads together and come up with a solution.

It is unwanted noise in the grow-room. Surely you tried like I did, and test out putting one of these vortex hurricane type fans in a box, stuff it with all sorts of different materials inside with the hope it would work.

I ran across some information outside this forum a long time ago talking about noise cancellation, but never had the opportunity to tackle it. The noise wrestling match I obviously lost.

https://en.wikipedia.org/wiki/Active_noise_control

https://en.wikipedia.org/wiki/Interference_(wave_propagation)

The two links I provided above is a good place to start when trying to understand this topic. It would be really neat if all of us growers worked on this project trying to find the right noise to counterbalance the one we do not want.

The whole idea is that everything on this planet has a certain frequency, and at a certain point on the frequency scale if played, it will cancel out the first one. It sure beats trying to put that fan in a four foot square box in the "hopes" it becomes more quiet.

As a retired audio engineer I would go the quite fan with sound absorption and isolation instead.

I commend the idea but so many variables to make simple circuit. To be sophisticated enough would be time and cost prohibitive. Well at first thought anyway. Anything can be done but you will put in more money and time than going another route.

Maybe use the parts from headphones adapted and interfaced to amp and speakers?

This will now occupy my mind all night. Thanks.

You should read about phase cancellation. Your last paragraph isnt correct. You'll get it.

Ok Thought for a second. I may try this in a month or so when I get my next room running.

I have a mic, mic preamp, reverse output polarity (switch phase 180 degrees) of preamp then off to amp and speaker.

Could be done. I never listened to noise cancelling headphones but if they can cancel jet engine noise it should do fine with fan noise.

Interesting idea but I still like the passive approach.

I think you may have to be in a specific spot in the room to noise cancellation? Equal distance from both sound sources.

Just when you think its simple it gets questionable again. Need to experiment.

I did phase tricks with nearfield monitors in the studio. Had to be in the exact right spot for total phase cancellation.

Damn you for getting me thinking again. Its been three years since I retired.

Soundman - I dont pretend to know anything about this topic, hence even my description was incorrect. But in order to understand it, and do something we must all start somewhere.

That is interesting, how you bring up sound canceling headphones, and applying this in the open space.

I was hoping to isolate the frequency of these monster fans, and use the principle to find another noise making object that had a frequency close to that one, hence it would cancel it out.

I used box fans, and these did help change the sound of the vortex fan. Maybe, or it might of been me just dreaming, and I created another noise that I was more pleased with.

But I felt that we all could work on this together, as you say, once a challenge comes to us, we want to push ourselves to find answers. It would be great if we found a simple solution, and all got to benefit from this feature.

The reason why I said everything on this planet has a frequency, I just did some research using the chart for light spectrum, and I learned that even sound belongs on this chart, so does a lot of other things. In fact if it has an atom, it has a frequency. It is interesting what they were saying about this topic, how our eyes get excited by this atom in our cones and rods inside our eyes. Atoms vibrate, they flip over, and do other neat tricks. Our eyes only detect one of these tricks is what they were saying so the chart for light spectrum lies in a much larger chart that includes almost everything.

It may be hard finding information on products which they list the frequency of their item, but I felt we should try and go down this rabbit hole, and see how far we can get. I am glad that you are interested in this topic, and helping here first. And hope all the other growers come and support us with their ideas, and research. That is what us growers are known for!

"In physics, interference is a phenomenon in which two waves superpose to form a resultant wave of greater, lower, or the same amplitude. Interference usually refers to the interaction of waves that are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency. Interference effects can be observed with all types of waves, for example, light, radio, acoustic, surface water waves or matter waves."

The above is a quote from Wikipedia, and below I included how others have used these techniques involving sound. But remember, this is not just a principle about sound, it works with other things too for instance, light frequencies. Now that would be an interesting topic as well for us growers here.

1936 – The first patent for a noise control system was granted to inventor Paul Lueg U.S. Patent 2,043,416. The patent described how to cancel sinusoidal tones in ducts by phase-advancing the wave and cancelling arbitrary sounds in the region around a loudspeaker by inverting the polarity.[4]

1950s – With U.S. Patent 2,866,848, U.S. Patent 2,920,138, U.S. Patent 2,966,549 by Lawrence J. Fogel, systems were created to cancel the noise in helicopter and airplane cockpits.

1957 – Willard Meeker developed a paper design and working model of active noise control applied to a circumaural earmuff. This headset had an active attenuation bandwidth of approximately 50–500 Hz, with a maximum attenuation of approximately 20 dB.[5]

1986 – Dick Rutan and Jeana Yeager used prototype headsets built by Bose in their around-the-world flight.[6][7]

Visible light is an electromagnetic wave, consisting of oscillating electric and magnetic fields traveling through space. The frequency of the wave determines its color: 4×1014 Hz is red light, 8×1014 Hz is violet light, and between these (in the range 4-8×1014 Hz) are all the other colors of the visible spectrum. An electromagnetic wave can have a frequency less than 4×1014 Hz, but it will be invisible to the human eye; such waves are called infrared (IR) radiation. At even lower frequency, the wave is called a microwave, and at still lower frequencies it is called a radio wave. Likewise, an electromagnetic wave can have a frequency higher than 8×1014 Hz, but it will be invisible to the human eye; such waves are called ultraviolet (UV) radiation. Even higher-frequency waves are called X-rays, and higher still are gamma rays.

For most of history, visible light was the only known part of the electromagnetic spectrum. The ancient Greeks recognized that light traveled in straight lines and studied some of its properties, including reflection and refraction. The study of light continued, and during the 16th and 17th centuries conflicting theories regarded light as either a wave or a particle.[6]

The first discovery of electromagnetic radiation other than visible light came in 1800, when William Herschel discovered infrared radiation.[7] He was studying the temperature of different colors by moving a thermometer through light split by a prism. He noticed that the highest temperature was beyond red. He theorized that this temperature change was due to "calorific rays" that were a type of light ray that could not be seen.


Radio - Collective oscillation of charge carriers in bulk material (plasma oscillation). An example would be the oscillatory travels of the electrons in an antenna.

Microwave through far infrared - Plasma oscillation, molecular rotation

Near infrared - Molecular vibration, plasma oscillation (in metals only)

Visible - Molecular electron excitation (including pigment molecules found in the human retina), plasma oscillations (in metals only)

Ultraviolet - Excitation of molecular and atomic valence electrons, including ejection of the electrons (photoelectric effect)

X-rays - Excitation and ejection of core atomic electrons, Compton scattering (for low atomic numbers)

Gamma rays - Energetic ejection of core electrons in heavy elements, Compton scattering (for all atomic numbers), excitation of atomic nuclei, including dissociation of nuclei

High-energy gamma rays - Creation of particle-antiparticle pairs. At very high energies a single photon can create a shower of high-energy particles and antiparticles upon interaction with matter.

Interesting subject. I'll be lurking.

Not going to be possible, well unless you want to stand in a very specific spot. It would be possible to create a null, but it would be in a very small spot in space, and would still require a lot of money and effort to achieve it. I have installed and setup commercial sound suppression systems, but all they do is create a lot of random waves, that when other sound waves bump into them, it distorts *weakens* them. These are used in buildings such as call centers or office spaces to keep the noise down from everyone talking on the phone. They work very well, when setup properly you can hardly hear the conversation two cubes away. All these amount to is a grid of speakers wired in two circuits, in a checker board pattern. You then have a pink noise generator that plays two different pink noises through both channels. This is setup to play about 65-70 db, and sounds like the 'woosh' from an air handler. The problem is, some people are sensitive to this type of noise. It causes fatigue, especially if you get up around 70 db, which is where it works the best. Personally these bug the hell out of me, makes my head/ears hurt. I would wear noise cancelling headphones while tuning and balancing these systems; but I would normally tune them at about 72-73 db to make sure the amps had enough power/head room, then I would turn the source volume down to meet the clients needs.

OldPhart said:

Not going to be possible, well unless you want to stand in a very specific spot. It would be possible to create a null, but it would be in a very small spot in space, and would still require a lot of money and effort to achieve it. I have installed and setup commercial sound suppression systems, but all they do is create a lot of random waves, that when other sound waves bump into them, it distorts *weakens* them. These are used in buildings such as call centers or office spaces to keep the noise down from everyone talking on the phone. They work very well, when setup properly you can hardly hear the conversation two cubes away. All these amount to is a grid of speakers wired in two circuits, in a checker board pattern. You then have a pink noise generator that plays two different pink noises through both channels. This is setup to play about 65-70 db, and sounds like the 'woosh' from an air handler. The problem is, some people are sensitive to this type of noise. It causes fatigue, especially if you get up around 70 db, which is where it works the best. Personally these bug the hell out of me, makes my head/ears hurt. I would wear noise cancelling headphones while tuning and balancing these systems; but I would normally tune them at about 72-73 db to make sure the amps had enough power/head room, then I would turn the source volume down to meet the clients needs.

Click to expand...

Well put. My brain operates at about 40% of normal due to illness. Hard to put my thoughts together and write them out.

Easier to do if standing in specific spot.

I also started thinking along what you were saying about using noise generator like white or pink noise last night later.

Just not feasible.

Interesting job you had. My room tuning was just studios and mix stages. I was Dolby and THX certified.

Ok. Fired up the old Pro Tools rig and did some white noise tests. I can get about a 30% reduction over a pretty good area and about 50% over a smaller area. That is with a perfect inverted track of white noise.

Not worth it in my opinion.

Maybe noise cancellation is a tall order to fill for our purposes here, but what about camouflaging an unwanted sound with another. Now the sound you want to remove now sounds more ambient. I used a box fan to make my vortex fan less noticeable. Have any of you here on this forum done something like what I did.