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Noise cancelling speakers?

by Owyn / March 7, 2007 12:34 AM PST

Looking for a way to reduce ambient (road) noise in an otherwise very nice front room. I want to use the room as a home office.

Was thinking about using active noise cancelling speakers attached to a small stereo as a solution.

I did a quick search and found these
http://www.sjgreatdeals.com/cbrhgs300.html

Any thoughts / recommendations?

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active noise cancelling sucks even in headphones!
by robstak / March 7, 2007 3:37 AM PST

i cant imagine that it'd work in a room. youd prolly have to be right in the middle of the speakers at all time, no?

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Sorry, You don't know what you're talking about
by Ravensblood / March 8, 2007 12:29 AM PST

I have the Bose Quiet Comfort 2 headphones, which are active noise cancelling, and they are amazing.

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I have a problem with wearing head phones for...
by Owyn / March 8, 2007 1:09 AM PST

extended periods of time.

The only style that I have found acceptable for any sort of extended use is light weight, wrap around the ear, loosely / partially inserted speakers.

That is why I was wondering about external solutions which could add a noise canceling signal to a standard audio signal.

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I didn't know that the speaker version existed
by Ravensblood / March 8, 2007 10:51 PM PST

but I was only replying to Robstak's comment re:headphones.

If you do end up looking for headphones, the bose are amazingly comfortable. try them out in a mall.

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How do you feel about in-ear?
by DangMI / August 13, 2009 7:26 AM PDT

I just (a week ago) bought active noise canceling Sony ear buds (MDR-NC22). Was very skeptical--made sure there was 30 days return and kept all the packaging. Depending on your circumstances, so far they've been amazing. I wanted them for mowing the lawn--they are very clear, I can actually stay at a lower volume level than with my canceling headphones, which I have to believe is kinder to the ears in the long run. Turned them off just to compare--totally just like white noise without them--hit the switch and all clear again.

On the other hand, took them into work--no effect at all on shutting out chatter. Have a fair amount of noise isolating ability--3 sizes of ends to help you get a good fit--but that was all. Actually a slight hiss if I turned them on so it was better to leave it turned off. I'm betting they'll be awesome on a plane. Will be a few weeks before I can test that.

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Sony ear buds
by Mesarose777 / September 1, 2009 6:21 PM PDT

I have neighbors who play very loud music with their garage door open and we live next door. Would these ear buds (MDR-NC22) block that kind of noise?

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Only if you use them to listen to your own music.
by Kees Bakker / September 1, 2009 6:28 PM PDT
In reply to: Sony ear buds

Then they will more or less filter out sounds coming from the outside.

Kees

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ha! knew i was right :P
by robstak / March 12, 2007 5:30 AM PDT

hehe. sometimes good ol fashioned stuff is better than new fangled technology! sometimes.

Wink

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The most important area for cancellation is...
by Owyn / March 8, 2007 12:58 AM PST

fairly small. ie. a 1m x 1m area centered in the corner of my L shaped work station and desk.

So, a relatively inexpensive localized solution could be of high value.

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Hmmm
by joe_news / March 7, 2007 6:19 PM PST

It might be easier just to sound proof the room. Or atleast take steps to increase its sound resistance...I don't live next to a highway, but if I did I'd totally invest in that because its totally worth leaving in a less noise polluted area.

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opps
by joe_news / March 7, 2007 6:20 PM PST
In reply to: Hmmm

By easier, I meant best.

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Subject title here.
by MedicineHead / March 8, 2007 4:42 AM PST
http://www.cobra.com/index.php?page=shop/flypage&product_id=225&id=1

There's the manufacturer's website entry. The speakers are made for the CB radios which means they probably will sound terrible for anything else. I also can't tell if they spit out noise reduction waves like what you're wanting, or if they're just made to cut the sound of a CB radio transmission. They definitely do not appear to be intended as stand-along noise reduction speakers, as they don't have their own power source.

They probably aren't what you're wanting.
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More information.
by MedicineHead / March 8, 2007 4:45 AM PST
In reply to: Subject title here.
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Thanks for the info...
by Owyn / March 8, 2007 5:13 AM PST
In reply to: More information.

Looks like the idea is not acoustically possible. I will have to look into other noise reduction options.

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Headphones is not a solution
by lousono / March 9, 2007 11:04 PM PST

There is a way to cancel noise with any speaker. This system is used on road repairs when noise is a problem for the neighborhood. It is using phase cancelling noise.When you have noises from different sources and you invert the phase of one of the source , there is no noise anymore. Keep searching, you will find something.

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acoustic noise reduction
by NeilFiertel / March 10, 2007 5:50 AM PST

Just try this and see if it helps...connect a microphone to an amplifier using the appropriate inputs depending on the type of microphone. I would suggest a stereo mic but a mono one ought to work also. Connect the speakers to be used as a noise cancelling setup reversing the leads of BOTH pairs of speakers so that the signal emitted from the speakers is out of phase with the input to the microphones. If the sound from the adjoining room is louder or softer after this setup is tested, try reversing back both speakers and if still there is room for improvement, reverse only one of the speakers. I suspect there will be some combination which will cancel some of the noise so long as you are in a constrained aread between or in front of the speakers. If you want to simplifiy the procedure, use a mono mic and one speaker. What you need to create is an out of phase field. It is unlikely that this method will cancel all frequencies but it might do all right with the mid frequencies. It is done at construction sites at times.

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Physics sets limits. Within those limits results are amazing
by inetdog / March 10, 2007 6:47 AM PST

The fundamental problem is that to cancel noise, you need to produce an exactly out-of-phase (opposite amplitude) signal at the ear.
The two ways to do that are to cancel the noise at the source and to cancel the noise at the ear.
Since sound has a wavelength which is right in the critical range (about 10 feet for 100 Hz, 1 foot for 1000 Hz, and 1 inch for 10,000 Hz the possibilities are affected very strongly by frequency.

To do a phase cancellation, you cannot just delay the signal, since that would either cancel or re-inforce depending on the frequency. So the phase reversal has to be set up so that the distance between the point where you measure the sound (microphone) to either the source or the ear is small compared to the wavelength you are trying to cancel.

For construction sites, you can measure the sound close to the SOURCE and put speakers surrounding it which generate a cancelling signal which reduces the amplitude of the sound waves at great distances. This only works if the frequencies of sound you need to suppress are low enough that your microphone and speaker spacing as small compared to the wavelength. For pile drivers and many other construction sounds, the low frequencies are the biggest irritant, so source-cancellation works.

For airplane seating, rock concerts (?) and home offices, the source is all around you so source-cancellationi does not work. Instead you put speakers and microphone both close (as compared to the wavelength) to your ear. This leaves the problem of how to make sure that the microphone picks up only the noise and not the speaker output. That is not hard to do in a headphone, but even then the medium price noise cancelling headphones do not do well much above 1000 Hz.

The limitations on speaker and microphone placement in the home office environment and the frequencies of the annoying sounds make the problem hard enough that I doubt that there are economical solutions right now.

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Yep. Found a very inexpensive partial solution.
by Owyn / March 10, 2007 8:29 AM PST

I put two layers of plastic heat shrink film over the (large) windows into the room. The film is designed to prevent heat loss but it turned out it also significantly reduced the road noise.

The glass in the windows was the main acoustic conductor.

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Noise cancelling devices for large rooms
by Jorge_Oria_y_B / August 13, 2009 12:13 AM PDT

Another solution, yet substantially more expensive is to install double or triple-layered glass windows with air or vaccum between the glass layers and plastic + wood framing (avoid aluminum, since metal framing is an excellent noise transmitter. These kind of windows are usually expensive and require a substantial amount of money, specially for large rooms with large windows. I live right next to a farm server company that operates 24x7 with over 40 air-conditioning ventilators installed on their plant roof, thus sending severe, constant noise pollution to the environment. My sleeping room is large with large windows and faces directly those 40 ventilators. Since I don't have such a large amount of money, I will try your inexpensive solution and see if that is enough for my room. Still if anybody is aware of a better, more practical solution, please help Owyn and me, please!

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fans and other devices
by beatmusic / November 15, 2009 4:13 PM PST

I live in a very quite neighborhood but late at night when all the traffic dies down I hear radio and TV broadcasts at various points in my small (very) efficiency apt. - I have noticed that having a small fan or even the motor from my refrigerator actually amplifies these sounds when the windows are closed - Winter time. Of course I live midway up a hill and can hear the individuals talking in a conversational voice four blocks or more across the valley. Anybody got any ideas why with the doublepane windows shut it gets louder. The acoustic vibrations? Maybe I can disrupt them by taping something onto the window or... It's not much but as a light sleeper if I hear Walter Cronkite (SP?) interview Nixon one more time...The most disturbing thing is that if I go outside there's total silence.

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What is your solution?
by fredhess / January 13, 2012 9:33 AM PST

What kind of plastic film did you use for the windows and where might I buy some?

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yea, what he said! Bose QC's...
by robstak / March 10, 2007 10:10 PM PST

Actually, I've used them and 2 diff Sony's (in ear and over the ear) and while you can tell something is happening, I bet you'll be disappointed. Passive noise cancelling is much better, and most of the internet sides with me. When I got my headphones, I did a lot of research on the intertubes and personal testing, and the little ammount of noise cancelling (or as I like to call it, white noise replacement) definately did not justify the increased cost to me. but again, that's just me. I'm not going to go as far as to say that you have no idea what you are talking about Wink

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Noise cancelling
by lousono / March 11, 2007 8:16 AM PDT

You're right Inetdog

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What about distant low frequency sound?
by Lichthammer / March 24, 2011 8:15 PM PDT

Rumbling from a train 1.5 miles away. I understand there would still be some frequency range but the corresponding wavelengths are still very small compared to the source distance. So it seems logical that phase cancellation within an affected room should work in this case. Yes? No?

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Noise Cancelling Speakers are a Dubious Concept
by PierreLaFrance / March 12, 2007 4:16 AM PDT

At one time, I thought that it was a good idea that nobody was pursuing, but found out that there's a reason nobody's going after it: because it's impossible to execute it successfully.
The basics boil down to perception.
For one to percieve actual noice cancellation, the actual 'noise' that you are percieving must be measured at the point of perception (i.e. your ear), because that noise will be different at different relative points in your environment. That's why the headphones work so well, because they're on your ear. Speakers won't work, because the speaker's point of perception is wherever that mic is located, and would be different for each person in the room. The only thing that I can suggest would be a 'white noise' generator, which can mask the noise through constructive interference, rather than cancel it through destructive interference.

But if you go headphones, go with the Bose QC3's - I've had the QC2's as well, and the 3's are lighter, less bulky, and actually work even better.

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Well actually. I think it could be done.
by Owyn / March 12, 2007 5:23 AM PDT

Each speaker would have to include a rear-oriented microphone and active circuitry to add an anti-phase signal to the original signal.

A simpler implementation would be stand alone powered "sound" generators. This approach would not be impacted by the power level of an additional "audio" signal. Best location of anti-phase sources would be as close as possible to the audio source, e.g. near a window.

I have, however, not been able to find that actually does this.

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Reduction not cancellation
by mjd420nova / February 22, 2012 9:05 AM PST

I think the best approach would be noice reduction and not cancelling. insulation can be installed and even wall treatments to kill offending, spurious noises. Window treatments can also help.

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