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By Cosima Donini
I want a sound filter for my windows. With all those smart people out there on the internet, it can't be so hard to make one. The sound filter works much like the mosquito nets I already have: It's cheap and you fasten it on the outside of your window. It'll keep out all the street noise, but it will let in the fresh air, which is especially good in summers.

Reward: I want sound filters for ALL my windows.
By Ray Deffry
Hi Cosmina,

That's good idea but I don't think it can be some kind a filter. Sound travels in air so if you let air in, you have sound. (i'm not a physcist, I could be wrong.

I talked with a physicist a couple of years ago who had this idea. He said that if you put speakers and microphones mounted outside your window, you could play the opposite wavelength sound back at the noise. You can cancel one sound with it's opposite wavelength.

Just a thought.
By R. Lloyd Nelson
That really could work on mostly monotonic, unchanging, ongoing noise like a lawn mower or leaf blower. However, variable noise like loud music would defeat such a system. It just couldn't respond fast enough.
By lusy
Whatever that's why they invented the "window!" there is never going to be anythiing that will keep noise out and let fresh air in... get a life!
By rhenry
Try this. Take two square fiberglass furnace/ac air filters and attach them to the outside of a standard box fan. Place it in the window and turn the fan on. The air filters should also help deaden the sound coming in.
By will
just snake it through a series of vents, padded vents, therefore it is muffles if anything. i believe its called an air conditioner right? just you cant see through it.
By monkey
Tricky one! But not beyond the realms of possibility. Negative sound would be the way I reckon.

You'd need some REALLY accurate (and fast) kit though. Sound travels at around 330 to 350 m/s depending on temperature and humidity, so if you put the mic and speaker 35cm apart you'd get 10ms to calculate the negative sound frequency. Then you'd need to trigger the speaker at exactly the time the 'street noise' sound wave reaches the speaker (some clever software and high quality kit should be able to do calculate this).

If any techies out there make one - can I have one please? :)
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By Michael D. Grissom
Negative feedback is how passive noise cancelling mics work. The sound recorded is inverted and amplified at the speed of light (not sound) and fed to the speakers -- no delays to calculate other than for those in the speaker and mic. The big three experimented with this sucessfully in cars (Popular Science article).

I think the best way to accomplish what you want to do is with the "white noise barrier" that was developed in the 60's (also Popular Science article) and tested at a Lazarus department store. The white noise is beyond the human hearing range but so powerful that audio freqs within our hearing range can't penetrate it.
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By CodeThumper
White noise would definitely be the way to go. Perhaps somebody could use the window screen to generate the white noise. This wouldn't eliminate the external noise but would probably reduce it significantly.
By nov8r
Keep the windows closed and design the cental air unit to pull in and filter fresh air when needed. Or a seperate air exchange system.
By Rishi
It should be possible to design a transparent muffler similar to the mufflers on the engine exhausts. This would be a series (Four?) of perforated, water clear, thin plastic sheets (Polycarbonate?). Each sheet will have random sized perforations which are staggered layer to layer.

Such a structure will muffle much of the noise, while allowing free access to air. In a dusty environment the screens could get clogged quickly though.

How transparent would the existing insect screen be is a matter for conjecture.

By DirtpatchSmacky
white noise is the onlly way to do this, Seeing as sound is just vibrating particles traveling in a wave, i think it would be possible to usea steel mesh screen to produce the white noise itself, just figure out a way to get it to resonate at the frequency desired. they have made flat panel speakers for quite awhile that vibrates a thin mylar film to produce frequency, and i recently turned an old hard drive into a speaker by feeding stero signals into the read/write arm, wich in turn fed the frequency to the hard drive disk causing it to vibrate and produce sound,, works pretty well actually.
By spuuut
Theres a product called silenceair available since 2005, it lets air flow in and out but has an inbuilt baffle that reduces the outdoor noise very well. The problem is that its only about 30 cms or 1 ft big, so youd need a lot to replace a window, bu they are transluscent plastic so light would come in. It ciuld be done but expensive and youd lose your view. Brett Curtis.
By InventR
The noise cancellation idea is the most logical & expensive solution.

Here's a cheaper proposal: A set of vertical blinds made of cork or some other absorbing material hung outside your window in parallel with a set of horizontal blinds of the same material about 8 inches apart.

Depending on where the noise is coming, adjust the 2 sets of blinds to act like a baffle as mentioned above. These blinds could be set in a frame which does'nt allow noise/air from the sides and have a deflective frame which bounces sound away on the sides.

Going a step further, deflector panels can be worked in conjunction with the blinds to get the best result.
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By swimmer
[quote="Anonymous"]Whatever that's why they invented the "window!" there is never going to be anythiing that will keep noise out and let fresh air in... get a life![/quote]

Impossible is nothing ! you cant say never . If we all say its never going to happen and " Go get a life "
Than there wouldnt be a car , or a mobnile phone , or a "Spoon " because those who didnt simply " get a life " invented these things.

When you think " is it possible " you can get to " Yes it is " , so dont be dull and just say " Get a life " .
somethings are ment to be sought of by people that are born to think and then Get a life !

You have just insulted all great inventors and scientists ...

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