Answers to Readers' Questions on Noise Reduction. Also refer to physics, acoustics, gasoline engines, muffler, combustion, music, loudness, filtering, acoustical materials, absorption, white noise, masking, Ron Kurtus, School for Champions. Copyright © Restrictions
Answers to Readers' Questions on Noise Reduction
The following 9 questions have been answered. They are listed according to date.
List of first 10 items
- Children oversensitive to noise and restrooms
- How does a muffler work?
- Developer removed natural noise barrier
- Will reducing air pressure reduce sound amplitude?
- How does amplitude of reflected wave vary?
- Dot matrix printer makes excess noise
- Wants to stop airboater noise in Florida
- Reducing noise in open office area
- Created a Noise masking CD
Children oversensitive to noise and restrooms
Question
November 14, 2008
Hi Your information was interesting. I am a therapist and work in the school system. I work with many children who have difficulty using the bathrooms due to oversensitivity to noise - the bathrooms are very loud - any suggestions for what we can do to modify the bathrooms? Thanks. Karen
- USA
16803
Answer
Restrooms typically have hard tile floors and walls to protect from water and for easy cleaning. Unfortunately, that also causes echoes and can make the rooms noisy.
Adding acoustic ceiling tiles is one thing to cut down the noise. Acoustic panels might by placed on the restroom walls and even on the walls of the stalls to reduce more of the noise. Of course the floors and anywhere water might be splashed must still be ceramic tiles.
Linoleum floors are better than ceramic tile for reducing noise.
I hope these ideas help.
How does a muffler work?
Question
March 14, 2008
can you tell me how muffler is working in technical way and which type of muffler is used now a days . types of muffler & which is better
sakib - India
15539
Answer
An automobile muffler works in a similar way as a firearm silencer works. In Europe, a muffler is also called a silencer.
The exhaust from the engine contains intense sound waves or noise. The muffler has a larger diameter than the exhaust pipe, thus lowering the pressure and temperature of the exhaust. This reduces the volume of the noise. By using a set of baffles within the muffler, the noise is further reduced.
Since there is such a variation in available products, I do not have information on the best type to use.
Developer removed natural noise barrier
Question
October 16, 2007
We live on a hill with a beautiful river view. Interstate 5 freeway is below us about a couple of hundred yards away. Recently a developer cut down the natural vegetation next to the freeway. It also had a natural berm, which he also leveled flat. Since then, we have had to endure constant freeway noise, and our deck outside is no longer enjoyable. Is there any sound science that can prevent the sound waves from hitting our home other than trying to mask the sound with white noise? We don't want to build a wall on our property which would block our view, either. If you are not able to help us, can you steer us in another direction to get help? Thank you for your assistance.
Brent - USA
14556
Answer
It certainly can be irritating to have a developer remove natural noise reduction, such as the vegetation and berm. Hopefully, you will build something that will block the noise again but not ruin your view.
You could wear noise cancellation headsets, but that would not be practical. Building a wall or planting a row of shrubs to reduce the noise are options but, as you said, they would also block your view.
You might try to find out what the developer has planned for the area to see if it is something that would solve your problem in the near future.
Will reducing air pressure reduce sound amplitude?
Question
August 21, 2007
It has been established that sound waves do not travel in a vacuum. Can one assume that by reducing atmospheric pressure that the amplitude of a sound wave will be reduced?
- USA
14231
Answer
One definition of the amplitude of a sound wave is that it is the variation from atmospheric pressure. The human ear operates by sensing pressure variations above and below atmospheric pressure. Thus, if the air pressure was reduced, the amplitude would be proportionately reduced. But the sound would appear just as loud to s person as it would at a higher air pressure.
Since sound is a compression wave, where molecules affect their neighbors, there is a point when air pressure is so low that the molecules are separated too much to affect each other as before. That is when you are getting close to a vacuum, and sound transmission starts to break down.
How does amplitude of reflected wave vary?
Question
January 30, 2007
How does the amplitude of a reflected sound from a particular surface depend on the frequency of the incident sound?
- USA
13013
Answer
The surface roughness and type of material will determine how much sound is absorbed and how much is reflected. The amplitude of the reflected wave will always be a percentage of the incident wave.
Dot matrix printer makes excess noise
Question
September 18, 2006
Hello sir,
This is Madhav from Mysore district, INDIA.
i am undergoing a project on noise reduction of dot matrix printer, where in i have to reduce the noise from 65 db to 45 decibel. other than changing the source or alterations to source which are the other techniques which can reduce noise?
It should be applicable for both low frequency and high frequency application. and which material should i use to design a printer cover which can reduce noise as well be cost effective?
which materials can i go for?
i am in need of suggestions and guidelines from you,
its my sincere request to you in this regard that please help me whatever you can.
eagerly waiting for your reply
thank you
madhav - India
11948
Answer
The following site will give you good information on reducing your noise by about 20db. Although the company is dealing with industrial noise, the principles should apply to your situation.
http://www.controlnoise.com/industrial-noise-reduction.html
They also have listings of noise reduction materials that are useful to your application:
http://www.controlnoise.com/transmission.html and
http://www.controlnoise.com/absorption.html
Installing the printer in a box with acoustical insulation should reduce the noise dramatically. Of course, you need to be able to readily access the printer and paper to be able to use the device.
Another suggestion is to contact the manufacturer of the printer. I know there are ready-made boxes that muffle dot-matrix printer noise.
I hope these ideas help you solve your problem.
Wants to stop airboater noise in Florida
Question
August 27, 2006
Please help!
Your School is wonderful! We suffer here in Florida from a perception that noise induced hearing loss risk is wimpy and a concept thought up by cry babies. We try to limit airboats to 90dBA 50 feet from the vessel. The actual typical noise level is well over 100dBA in the 110 range and higher.
Local law enforcement is working in our area, however state wide there is a perception that air-boating is romantic, kind of like "Cowboys" and therefor not to be messed with.
Not wanting to live in our homes with ear muffs on 24/7, we think perhaps noise canceling might provide relief. Note, the air-boaters use ear muffs and refuse to use effective mufflers. Most engines are automotive V-8 design and are used with open flex-pipe tubes. The propellers are usually under pitched allowing tip speed at and above mach 1. There is no limit as to how close these vessels can come to homes and people. They are able to run on water, and dry land for extended periods and distances.
LRAD focused sound systems appear to lend hope to home owners plagued by airboats with no or lacking mufflers. Engine noise and propeller noise may be able to be canceled out in a protection zone around a home.
State law enforcement is lacking and actually supportive of the macho loud nature of the airboats. The FWC (Florida Fish and Wildlife Conservation Commission, And the DEP are the world's largest owner/operators of airboats. By creating loop-holes in the law they are able to continually keep airboats loud.
The public may be able to switch from or at least argument efforts to enforce noise law by blanking out noise in a focused long range sound wave energy frequency cancelation.
Any thoughts?
Best regards.
Don - USA
11778
Answer
Just as automobiles are required to have mufflers to reduce and almost eliminate the noise level, airboats should also have a similar requirement. It defies logic that they are allowed to make so much noise that the air-boaters wear earplugs but there is no concern for people living around the water.
That type of noise is not only irritating, but it can also cause hearing loss, especially among children. People living near waterways with excessive entertainment vehicle noise can suffer from stress levels that affect their health and quality of life.
There is no way to cancel out the noise except to constantly wear noise cancellation headsets.
The best thing to do is to try to force some anti-noise legislation, at least in the area where you live. Get together neighbors that also may be concerned and irritated about the noise. Petition you local government representatives and even state representatives. The EPA once had a Noise Control agency, but that was eliminated. See: http://www.nonoise.org/news/1990/aug26.htm.
Note that the EPA is concerned about airport noise, so they may also look into air-boating noise: http://www.epa.gov/fedrgstr/EPA-GENERAL/1996/July/Day-23/pr-23525.html.
Also see: http://www.nonoise.org/news/1998/nov22.htm. The article half-way down the page talks about Florida legislation on air-scooter noise.
It may be a lot of work, but I think the effort to stop the noise would be worth it. Best wishes in your efforts.
Reducing noise in open office area
Question
April 19, 2006
Dear Sir ,
I would like to know more information about device or systems that are used in large open offices where many persond are sitting in open however the talk/sound/noise of each other is not disturbing others . I understand some additional waves or frequencies are spread in romm which are not heard by persons but will help in reducing noise ?could you please send me some more details on this method/subject .
Thanking you .
SANJAY - INDIA
10880
Answer
In large open offices, you want to have dividers that are insulated with a soft material. Acoustical ceiling tiles are good to reduce noise. Drapes hung by the window also reduce noise. The idea is to have as much sound-absorbing materials as possible and eliminate straight paths for the sound to travel.
There are no devices or systems that will cancel out the sound in such a room. Sound-absorbing materials must be used.
Created a Noise masking CD
Question
January 17, 2006
Hey, I just ran across your site, nice work! I wish I had found it earlier.
I was in a really bad neighbor noise situation for several years, I lived in an apartment building in a 1st floor unit with a very large (grossly overweight) family of 5 above me and a wanna-be rap star with a thumping home studio beside me, needless to say I didn't get much sleep. The police and management were of no real help, so, as a result I used my background in composition and audio engineering and developed a sound masking CD that I am calling Soniscape. Basically, you play it on your stereo in a loop and it masks out noise pollution with natural sounds and creates a peaceful environment. It sounds like a mountain stream. There's some info and an audio sample on my site http://bretthouston.com/soniscape.html
I finally moved a few months ago to a nice peaceful place in the mountains and thought I wouldn't need it, however when the raccoons would run across the roof at 4 am it made me remember the horrors of my old place so I started using it again to sleep without being disturbed. I have gotten to where I bring on trips with me to mask out neighboring guests in hotels or my girlfriend that snores like a grizzly bear.
I decided that since it worked so well for me that I would make it available for other people. Id be happy if you could include a "Soniscape" link on your site and pass on the info to anyone who may be interested. I'd also like to include a link to your site as well if that's ok?
Cheers
Brett - USA
9715
Answer
I added a link to your site from our page on Noise Reduction at:
http://www.school-for-champions.com/science/noise_reduction.htm
That would be great to add a link to our site.
Best wishes with your CD.
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Answers to Readers' Questions on Noise Reduction