Acoustic cloth

Please note these boxes as they come are not waterproof. I cast a seal with silicone - I am sure a conventional bath sealant would work as well as the mould making rubber I used.

I used the smallest box from Really Useful Products http://www.reallyusefulproducts.co.uk/uk/html/onlineshop/rub/b00_07litre.php in recycled black and a normal hot glue gun to attach the cloth. The trick is to ensure you get a really good bead of glue adhering to the plastic, then place the cloth over it and use the tip of the hot gun to push it into the glue. Not the best method and a bit tricky but it worked. I tried other adhesives (cyanoacrylate) but it didn't adhere well. I haven't tried some other plastic cements.

Hi David Martin,

I would appreciate if you let us know what's the box's brand and which glue did you used to fix the acoustic membrane? Thank you!

Best,

Noelia

That would do nicely!

Like this? http://www.pauzuolis-rc.com/rc-shop/building-materials/mylar-film/mylar-film-3-mk It would be easy for me to swap out the acoustic cloth for the mylar on my boxes.

s by moving it to and fro, not magically passing through it)Absolutely not a crisp packet - but also not very readily available. This stuff is thinner and lighter than clingfilm and is used for the diaphragms of ultrasonic capacitance microphones that work to over 200kHz. Small mass means that the sound waves have to do less work to move it (and sound transmission across a diaphragm is done by moving the diaphragm to and fro not by magically passing through it) and therefore sound attenuation is minimal. Clingfilm is an alternative but is about 12micron and therefore more massive. Anythin in the form of a grid or mesh tends to attenuate high frequencies and cause dips and peaks in the frequency response, and directionality at lower frequencies.

"I have tried making some bat recordings using a film of 3 micron aluminised Mylar over the microphone port " - does any one else read that as 'I put it in a crisp packet'? :)

Here are a couple of mine. They are sufficiently waterproof to be out in the rain.

And a more distant shot

Below are some photos of the container i have made using a small plastic craft box, cheap make up sponge and bird fat cage, approx £6. Still need to cut hole for microphone and acoustic cloth

I have tried making some bat recordings using a film of 3 micron aluminised Mylar over the microphone port and even sounds up to 192kHz are still coming through and the results seem comparable with a Petterson M500-384 although the noise profile is not so good. Details of how to see the recordings are in the 'sample recordings' thread.

Been looking into how I could do this -I think paypal and to cover costs would be (for UK) £1.20 for one sheet inc 1st class P&P and 30p per additional sheet, of course, if you are close to Bristol UK you could pop in. The sheets have filing holes and laser cut numbers so the max size of virgin sheet is 12x12 cm. My email is david at brownfamilymail.co.uk so you can drop me your address and I can send you a paypal invoice.

Also keen to try one. I think I will only need a tiny amount for my needs. Please let me know if you would be willing to sell one on

Please can I try one will pay for it. FRAN

The samples have turned up and I have 41 pieces of hydrophobic cloth. I may be in the market to distribute some.....

Will do

Thanks Fran, I've ordererd a sample of the water proof cloth.

Thanks Fran, very cool cloth. It would be great if you could post a picture of your finished housing.