How to make a soundproof air vent

[stolenband]

Hello to all. I have started getting stuff into a large room for recordings, and figured out that i am in need to provide ventilation to an air furnace. The route of the air at the moment is to travel through doors that have vents and be open to the whole house. Is there any way i can redirect the air intake or my most probable option... to make a soundproof vent to install.

I was thinking about a box that i would place strips of wood in so the air would have to go around several corners and the sound would be deadened.

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something like the text diagram if the parentheses were openings. I live with several people and would like to make life easier for them.

Thanks

[WithTarragon]

Turns out this is a trickey thing to do.

You are on the right track with the idea of baffles. The rough rule of thumb is that you will get a 3 dB loss everytime the sound has "to go around a corner". This is for the speech frequencies. The lower freqs are tougher to control.

There is a prduct called "Q duct" that you should look into. When you get folks to consult on this, they need to understand your expectations in terms of how much attentuation is required and how low in freqeuncy do you need to go.

[Alex from Oz]

This product might suit

Silenceair

Cheers,

Alex

[geraldfryjr]

The method is very simple realy.
Do you know how to make a simple labyrineth speaker cabinet?
Or a transmission line speaker type cabinet?
In order to reduce this type of noise, is too use a series of baffles in the circuit of the of the air system feeding the air into the room of question.
Hope that helps. jer

[Ron E]

Originally Posted by stolenband

I was thinking about a box that i would place strips of wood in so the air would have to go around several corners and the sound would be deadened.

|---------------()--|
|--()---------------|
|---------------()--|
|--()---------------|

something like the text diagram if the parentheses were openings. I live with several people and would like to make life easier for them.

That will help some, it would be even better if you made the baffles out of perforated metal surrounding Corning 703. This is how large duct silencers are made. You might want some "turning vanes" at the corners or you might get very little air flow.

I've been in a control room made of all perf inside with hard fiberglass underneath (solid sheetmetal outside) and it was pretty strange - not quite anechoic-unsettling, but very, very dead. It was a lot quieter than the factory floor, let me tell you.

[martin clark]

These things are manfactured in a range of sizes and dBW ratings and available off the shelf from any duct supply house - google 'crosstalk attenuator'. They're used where air supply / return ducts pass through acoustic-rated partitions to limit noise transfer via the air in the duct. This will be cheaper and more effective than a DIY effort. Build into /onto teh external wall, add insect mesh on each end and you are done.

If you really want to build your own I can share some builder's work details I've done before. Basically, the labyrinth idea is about right, you need to line the sides with mineal fibre slabs leaving the air path through the middle. Bulky! About 30dB loss is the best you can hope for like this.

[WithTarragon]

The products listed above may not be very effective for your project. But you have not yet told us your goal in terms of attenuation and bandwidth.

The 30 dB number is for some of the better commercial products, and please note that is most likely a "dBA" measure. The difficulty you will have is at the lower frequencies and any impact sounds. Again, what are your expectations?