Answers to Readers' Questions on Noise Cancellation. Also refer to sound, physics, acoustics, sine waves, compression, phase, ear, earphones, microphone, detector, interference, waveform, Ron Kurtus, School for Champions. Copyright © Restrictions
Answers to Readers' Questions on Noise Cancellation
The following 89 questions have been answered. They are listed according to date.
List of first 10 items
- Father wants to take over science project for daughter
- Solutions available for noise cancellation
- Could noise cancellation mask snoring sound?
- Protecting from hearing loss
- Doing a physics project on noise cancellation
- Uses noise reducing headphones when mowing lawn
- Send catalog on noise cancellation
- Need a device to cancel noise outside open windows
- Noise cancellation in automobiles
- House near highway with much truck traffic
Father wants to take over science project for daughter
Question
October 27, 2009
hello, i am a father helping my daughter do a science fair project. when i was in college, i saw a project in sound cancellation. it consisted of a large T shaped base. at the top ends of the T were speakers. they would spin the T and you would hear the sound amplified, and then completely canceled.
i would like to use this sort of idea for the project. my question is, do i have to have a specific sound? and when i make the unit, does it have to be a certain size? so that i can ensure the sound waves will cancel and magnify as i twist it around.
can you give any advice on the best ways to construct it for a school science fair environment?
thank you for any help you can give me.
JR - USA
18584
Answer
It sounds like an interesting device. My guess is that the T would spin at a rate such that the sounds would be in or out of phase.
Although the device may be "cool" if you can get it to work, I don't think it is appropriate for her science fair project or is it a real learning experience for her. The idea for a project should come from her studies, observations or questions. They usually have guidelines concerning hypothesis, research and conclusions drawn. Often a simple idea that is well thought-out and executed is better than something complex that another person makes.
Perhaps you should ask your daughter if she would prefer to do something herself with your guidance or if she wants you to take over and make something for her to display. This way you can tell what she really wants.
I hope you don't take offense by my suggestions.
Solutions available for noise cancellation
Question
October 13, 2009
I just read through your Q&A section, and I am surprised that you are so dismissive of the use of ANC in automobiles and other dynamic environments. ANC has arrived, and is a very feasible technology for automobiles and many other enclosed space. The method for addressing active noise cancellation in a cabin is much different from that of your typical headphones but is still effective given the correct circumstances. I would be willing to share with you an article I wrote, discussing the finer points of this difference and even allow you to add it to your website if you wish.
Saying it is not effectively is patently un-true though. We just completed an installation in a locomotive in England where we achieved a 9 dB / 4 dBA reduction around the engineer and fireman. The Chevy Equinox employees an ANC system so that they could lessen the amount of insulation used in the vehicle while maintaining the same ambient noise levels and increase fuel efficiency. The 2010 Acura ZDX will be employing ANC for the exact same reason.
I hope this email will help update the information on your website.
Additionally; I have requested a time or two in the past to have my company NVH Technologies added to your list of Products. Is there any reason that has not been done?
I look forward to your response.
Best Regards,
Taylor - USA
18496
Answer
I'm not dismissive about the use of active noise cancellation (ANC), but I realize it is a very difficult problem to solve. There is a terrific demand for ANC in all sorts of noisy environments, but I haven't seen any reports that the method has been used in many places, even in automobiles.
I would be glad to take a look at your article and perhaps add the material to the website to update our information.
Sorry about not considering your company. After checking your website, it looks like you provide some of the solutions that people have been looking for. I added a link to your site and our resources section at:
http://www.school-for-champions.com/science/noise_cancellation.htm
Could noise cancellation mask snoring sound?
Question
October 9, 2009
could this be used to mask snoring sound
- Canada
18466
Answer
Unfortunately, noise cancellation devices are usually clumsy headsets. However, you can mask annoying sounds with a white noise generator. See:
http://www.school-for-champions.com/science/noise_reduction.htm
Protecting from hearing loss
Question
June 17, 2009
Does active noise cancellation technology really protect you from instant or progressive hearing loss, or simply prevent you from hearing the generated sound?
Norman - USA
17919
Answer
The main purpose of active noise cancellation is to prevent hearing distracting sounds, but it certainly could be used to to protect from hearing loss in noisy environments, such as those experienced by factory workers and airline employees.
It seems that most of those employees use effective ear plugs, such as made by Sonomax, to protect their hearing.
Doing a physics project on noise cancellation
Question
April 18, 2009
I'm currently doing a physics project on noise cancellation
We got the liberty of picking anything we wanted and I wanted to do it on this because I bought the Bose Quiet Comfort 3 Acoustic Noise Cancellation Headphones and I found it really interesting how the noise drowned right out. The information you gave me was good, but I was wondering if there were formulas with soundwaves to prove this stuff rather than just graphing and explaining. I need to give a 3 minute explanation to my teacher sometime in the next month or two about this. So I just basically wanted to know what is the science behind these particular headphones, how does it work and why does it work. I have the fundamental concepts of reciprocal waves cancelling each other but I can't explain any further than here's a wave and look it cancels end of story. I need more so any help you can give would be greatly appreciated. Thanks in advance,
Nathan
Nathan - Canada
17626
Answer
Active noise cancellation depends on electronics to reverse the waveform in close to real time. The problem is that the sound waveform is highly complex. You could use Fourier analysis to break the waveform into its components. To a degree, this is what the electronics does.
A good technical article on the subject is "Active Noise Reduction Headphone Systems" at http://www.headwize.com/tech/anr_tech.htm
The same website also has "Build These Noise-Canceling Headphones" at http://www.headwize.com/projects/noise_prj.htm, which shows the circuitry involved. Both article should be helpful to you.
As far as an experiment to do goes, use a tone generator and measure the input amplitude and output amplitude of the headphones over a range of frequencies. This would verify the effectiveness of them.
Best wishes on your project. Let me know how things turn out.
Uses noise reducing headphones when mowing lawn
Question
April 14, 2009
Honda and Acura do import cars with ANC however I have never been able to hear any appreciable quiet in a test drive, that being said they may be noiser cars without it.
The quietest car I have found is a Lexus LS, so quiet that the noise you are left with are truly low frequency, and sometimes seems very pronounsed,( this may be due to the lack of high mid/high frequencies masking the lows). One can speculate ANC in a lexus would be about as quiet as one would want.
If you have any advise on where, how one could put ANC in a car, please let me know. I recently purchased a set of noisebuster brand passive/active headphones for cutting the grass etc. , these are as good or better then most aviation sets I have tried and cost only 150.00. Do you thing these could be adapted to work in a car, utilizing the AUX input on the car sound system.
Thanks for your interest.
Frank
Frank - USA
17603
Answer
Active noise cancellation is not really effective in a changing environment, like an automobile. It is a nice effort, but the technology isn't sufficient yet. Sound insulation in a car like the Lexus is much more effective that electronic cancellation. But it might help with reducing or eliminating the low frequency noises.
It is good to know that your Noisebuster headphones reduce the noise when you are working outside. You could wear such headphones in your car, provided it is not against the law. There is often concern about not hearing the siren of emergency vehicles.
Hopefully there will be improvements for ANC in future automobiles.
Send catalog on noise cancellation
Question
March 8, 2009
HELLO
I WANT INFORMATION ABOUT NOISE CANCELLATION ACCTIVE IN OUR COMPANY BECAUSE IT VERY NOISY AND TO BUY SYSTEM ACTIVE NOISE CANCELLATION WHAT WILL DO ME.
PLEASE SEND FOR ME PRICE AND CATALOGUE ABOUT APPLIED MECHANISM.
THANK YOU
SINCERELY YOU
MOGHTADA - Iran
17408
Answer
I am sorry, but this is an educational website, giving information on the subject. We do not sell products.
See the Resources on:
http://www.school-for-champions.com/science/noise_cancellation.htm
to find companies that sell noise cancellation devices.
Also see:
http://www.school-for-champions.com/science/noise_reduction.htm
Need a device to cancel noise outside open windows
Question
February 15, 2009
This is surely an area of opportunity. My personal need would be for a device that would 'cancel' ambient noises outside my apartment window, thereby allowing my wife to sleep with the window open during the night. The further upside would be the abundance of fresh, cooling air, providing a healthier sleep environment. Do you know of any such device, or of any potential source?
Thanks very much for the chance to ask this question, and perhaps to improve my(our) future sleeps.
Thomas
Thomas - Canada
17278
Answer
A device to cancel out noise is something that many people desire. Unfortunately, the only effective ones are headsets. An area to look into is noise reduction, where you can cut down the amount of noise that reaches you, as well as masking noise, so that it is not so annoying.
See: http://www.school-for-champions.com/science/noise_reduction.htm for information on that subject.
One thing you can if you move to another apartment is to try to get one that is not exposed to obvious sources of noise. It certainly is a consideration to make.
Noise cancellation in automobiles
Question
November 15, 2008
how can i receive any information a bout the noise cancellation in automotive?
hamid reza - Turkey
16805
Answer
Most automobiles have noise reduction from absorbent materials inside the car. As far as a know, only Honda Motor Cars had tried a noise cancellation system in their cars. Apparently, it did not work too well.
Right now, only headsets work to cancel out noise.
House near highway with much truck traffic
Question
June 24, 2008
We have a house (wooden) very close to a major highway (20m) and trucks drive through at 80 to 100 kph and make a lot of noise and vibrate the walls. What is available to counter this sound. Is there a wall design which will direct sound in such a way that it bounces back to the road and possibly crosses over thereby reducing or canceling the noise in the building? I have seen eggboxes on the internal walls used in studios to absorb sound - and wonder if there is any way this might help (ie fixing egg boxes to a wooden wall between the road and the building?
Many thanks,
Hans - New Zealand
16135
Answer
Many cities install concrete walls between the freeway or highway and houses, where they are close to the road. Some are made of concrete blocks, but I've also seen a form of corrugated concrete material. Unfortunately, that probably would be fairly expensive for you.
Instead of a concrete wall, you could put up a high wooden plank fence in a slight zig-zag shape to reflect some of the noise. Even planting high, dense bushes would help to diffuse the sound somewhat.
It is a difficult problem, since the road noise from the trucks can be very disturbing. I hope these ideas help you in finding a solution to your problem.
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Answers to Readers' Questions on Noise Cancellation