Traffic Noise Coming Through Windows

Hi Ted,

I just discovered your very helpful site. I have a question. We recently purchased a ten year old home that has good quality, double glazed vinyl windows (the operable kind, single hung, vertically opening). We hear traffic noise in our master bedroom, which faces the street and I am looking for a method to reduce it as much as possible. I had thought of buying some heavy fabric roman shades that would fit inside the frames, but doubt that this approach would do much. I am not sure if the sound is simply being transmitted from the outer pane, through the air space and onto the inside pane or if it is getting through the area where the window slides in it’s frame. Do you have any thoughts on this? I am am a Mechanical Engineer but have no real knowledge in acoustics.

Thanks very much for your thoughts. I hope you can shed some light on this.

G. Powell

Mr. Powell,

Soundproofing windows can be a little bit tricky, but there are two pretty basic and simple things to keep in mind when you are trying to block sound. I’ll throw you a little curve ball at the end, but want to go through a couple things first about how to soundproof windows.

The two most important things to keep in mind when you are dealing with a sound transmission issue are eliminating ANY common air spaces and increasing the amount of mass/density in between your noise source and a potential “listener”. A 1% air gap in any kind of a noise barrier will leak 30% of the sound from one side to the other, and a 5% gap will allow for a 90% leak. If you consider that sound travels through air, you can quickly see how even a tiny gap will allow for a significant amount of sound transmission. Additionally, the more mass and density that you introduce as a sound barrier, the weaker the pressure wave will be after it passes through the mass.

I have one product for each topic above:

Climate Seal™ Acoustic Series Window Inserts

Acoustical Quilted Curtain

The Climate Seal™ Acoustic Series Window Insert is going to perform the best, be the least visually intrusive as well as the easiest to install. Furthermore, because of the increase in thermal performance of the window, it will also pay itself off in a few years. It is, however, more expensive than the other option for soundproofing windows. Basically, this system is a “snap into place” window that is held in place by a magnetic bellows system similar to the seal around your refrigerator door. You (or a local installer) will cut and screw a thin metal ‘L’ bracket around the window frame to create a metal surface for the magnets. Inside of the magnetic bellows perimeter will be a ¼” thick piece of clear plastic called Lexan. This plastic is scratch resistant, fairly light weight and will never yellow. The only consideration will be the cleaner used to clean the window when needed, but we can talk about that if needed.

This window was designed to be a re-usable heating and cooling thermal product but because it does such a good job at eliminating any kind of draft or common air space between the inside and outside of the house, we found that it does a very good job at blocking sound as well. The price for each window will depend on the size of the window, but I usually suggest people use a $23-25.00 per square foot ballpark price Shipping is harder to estimate, and usually the best way to get them to a job site is by putting them onto a plywood pallet and sending them on a truck. Estimating performance is also a bit of a hard subject because of the variables involved. The performance of the window will depend on the sound transmission rating of the casement window as well as the decibel level and frequency of the noise source. It will also depend on the ambient level of the room in which the windows are being installed.

The other product that has been used in similar situations to soundproof windows is the Quilted Curtain product. This is not a curtain in the traditional sense of the word as it can not be pleated up like a hospital curtain or a min-blind. This is more of a fairly rigid acoustical panel. It originated as an industrial grade product which could be used to enclose a noisy machine in a manufacturing plant or be used as a movable sound wall. It is usually fairly challenging to get it into a residence not only because of the look of the product but also because of the weight. The “active ingredient” in the curtain is an 1/8″ thick, 1lb. per square foot Mass Loaded Vinyl noise barrier. On either side of the vinyl, we place a nominally 1″ thick piece of fiberglass, and then quilt the whole product in a heavy duty vinyl. We pound grommets through the top of the panels to use as a mounting point. Because these curtains weigh about 1.5lbs per square foot, they are cumbersome and not easy to move. Usually when they are installed, they are left in place all of the time. These are also made on a per job basis, and I usually tell people to ballpark for a $12-14.00 per square foot price.


  1. Antebi Rahamim

    I am an Electronic enginner and I am trying to find some generic solution for the noise problem in my house
    What about using active methods to reduce noise ,such as receving the signal from an array of microphones posted in front and repeating the same waveform deviated by 180 degrees after amplification through loud speakers posted at the rear? it seems that this method could provide a “zero” acoustic level at the window aperture
    I will be happy to hear your comments
    Best Regards Rahamim

    • Ted W

      If you find a way to do this, please share the technology with us. I understand the concept because people have been asking me about this for years, but by the time noise gets to a microphone and processed to determine the “opposite” wave, isn’t it too late? Sound travels at about 1160 feet per second, so by the time a speaker would be able to play an “opposite” wavelength, the sound would already be heard by a potential listener.

      But, I’m not an electrical engineer, so I don’t know what is possible in that field.


  2. Sush

    Try using sound proof windows instead. I was suffering from same from later i came to know that sound proof windows are made of 2 glass with vacuum inside it which helped me a lot

  3. Jon

    Ted, I believe what he is suggesting is to record the incoming sound with speakers in front of the window, and then have an “180 degree inverted” waveform projected from behind the window to “cancel” the incoming sound. As far as I understand acoustic physics, this is not possible (ie. an inverted sound would magnify the range of sound in frequency and the range of sounds out of frequency with one another would have no effect, but both would be heard. That is to say, there is no such thing as “negative” sound, to my knowledge. Imaginative concept, but not realistic.

  4. Gary Metcalfe

    “Negative” sound IS possible, but not easy!
    Simple proof is to take say an 8″ speaker (just the speaker) and play some “bassy” music through it.
    Then put the speaker either in a cabinet, or in the centre of a piece of wood about 4 feet square.
    The 1st scenario will be very lacking in bass, the 2nd, much “heavier”.
    This is because the same sound waves come from the back of the cone, but 180 degrees out of phase…so cancelling the sound!
    Bit more electronics required, but it’s been used in high-end cars for years….both to cancel the road noise, and also to change the tone of the exhaust!
    A microphone(s) pick up the noise in the car, filter out the required frequencies, and then feed a signal out-of-phase to that to cancel certain parts out.
    It’s not so easy as saying 180 degrees, as there is a lag in the electronics, so it could be 150 or 230 or?!?!?

    It’s also been tested at very high power levels on helicopters…the “whisper mode” (yeah, it’s NOT a SciFi thing!)
    The noise from a ‘copter is due to the down pressure from the blades…match the frequency of that and feed the inverse of it at high enough volume..and the 2 cancel.

  5. Vidmantas

    First of all what do you need to know installing windows is its sound insulation index Rw. And it should be chosen such adequate to outdoor noise level. As higher oudor noise as higher should be Rw, dB of the window. High value of Rw is for example 42 dB. so You should to know what is performance of installed window

  6. ScottO

    Yes noise canceling is possible. Is it easy?, Maybe. My subwoofers from “Rythmic” have servo corrected woofers. As in 2,300 time per second they are corrected by a processor that see’s how far the woofer is moving “underthrow, correct throw , overthrow”, AND what frequencies are being made by the cone. Sound travels very slowly compared to electrical signals that supposedly travel at roughly 1/40th the speed of light. So the processor has plenty of time to correct.
    The same thing could be done to noise cancel utilizing “Rythmic’s” or maybe “Velodyne or Martin Logan’s”, processors if adapted to the frequencies you are trying to negate. Using a mic or group of mics and a few small full range speakers pointed in a curved array per their horizontal dispersion specs. so that the waves overlap a bit. “Vertical dispersion will already be there.” and a “good” amplifier, which can amplify without much distortion,
    I have been thinking about this for awhile but haven’t really the time nor inclination to carry it though to it’s logical conclusion. Which would have been a “stand alone”, noise canceling unit you could point and have a 180 degree “cone of silence”, basically that canceled all noise in that 180 degree area. It “would” work whether you lived near a race track, ballpark or a busy highway. It would not work on the out of phase reflections coming back though your given area, but the Db from that would most likely be negligible anyway. I hope this information helps someone.

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