©2019 Open Acoustic Devices

Apr 12

Summary of enclosures to date

2 comments

 

Hi AudioMothers,

I’ve been doing some research towards making enclosures for the Round 6 AudioMoths that we have on order. For the benefit of others, here is a bit of a summary of some of the attempts that I've seen so far:

(1) a zip-lock bag (the ‘base model’). This is rain-shower-proof (but not fully weatherproof, I don't think) and the sound recording doesn't seem to be affected by the thin plastic over the microphone. Simple, cheap, lightweight.

(2) a little click-lock container with a hole drilled in it for the microphone to listen out through, and some Scotch tape over the hole. In this example the container wasn't watertight to begin with. https://www.openacousticdevices.info/support/enclosures/box-for-audiomoth

(3) using a click-lock container (with a drilled hole) and some clingwrap over the hole. Not certain how waterproof the end result of this was. https://www.openacousticdevices.info/support/enclosures/an-alternative-case-for-audio-moth

(4) using an electrical junction box (with a drilled hole) and some hydrophobic cloth. Still not fully waterproof. https://www.wildlabs.net/community/thread/554

(5) using an IP54 ( Ingress Protection: 5 = dust protected and 4 = splashing water protected... see https://en.wikipedia.org/wiki/IP_Code) electrical junction box (with a drilled hole) and waterproof acoustic membranes (stickers). I think I like this the best out of all of these because the boxes have moulded eye-holes such that you can attach with cable ties and it all sounds reasonably water-tight. But the stickers are really expensive and didn’t always hold-up in field conditions.

https://www.openacousticdevices.info/support/enclosures/case-for-audiomoth

(6) adulterating a waterproof/dustproof case. This seems only a step or two short of putting a tiny detector in a shipping container for deployment. But it might be good if security is an issue. (I think I'm going for the if-I-hide-it-then-no-one-can-see-it-and-therefore-can't-steal-it approach.) https://sites.google.com/view/audiomoth/housings-or-cases/samson-case

(7) a custom 3D-printed case. Not sure how you print the rubber seal? Is that possible? Also not clear how the microphone has access to the outside world?

https://www.thingiverse.com/thing:3292311

 

(8) the Open Acoustic Devices’ acrylic case. In the pipeline, it seems. See these threads:

https://www.openacousticdevices.info/support/enclosures/about-protective-measures

https://www.openacousticdevices.info/support/enclosures/possible-case-for-audiomoth

While not a full solution, there was theoretical discussion to suggest the addition a ventilation port such that any condensation can evaporate out of the case. I don't know what to think about this. If the air holes faced down and were underneath some sort of sheath then it may work? Provided that the case was always mounted 'right side up'. But, presumably, this would also let humid air in? https://www.openacousticdevices.info/support/device-support/audiomoth-housing

I have also contemplated popping a desiccant in the case, just to keep things happy and dry (and to protect from condensation etc. on the inside if the case is in the cool, then the sun, then the rain, then the full sun again, then the cool etc.). Silica gel baggies seem simple and cheap and the way to go. This has been mentioned a few times in the support forum here too.

 

So, for our planned study (in south-western Australia – and the climate that we have here), in summary, I think we need to use an enclosure that: (i) is generally weather-resistant (i.e. rain and wind but not necessarily immersion; and we don’t experience frost, snow etc. or crazy, prolonged humidity either);

(ii) has loops through which cable-ties (or similar) can be threaded for securing the enclosure to a branch/stake etc.; (iii) has a hole through which the microphone can hear the outside world - but have this hole weather-proofed in some way. (I think this weather-proofing of the microphone port is where all the challenge is in any of the above systems).; (iv) is reasonably easily open-able such that we can get the AudioMoth units in and out without too much fuss (we’ll be doing this on a regular basis); (v) has enough room for a backup bag of desiccant on the inside; (vi) is cost- and time-effective to construct.

If anyone has any other input at this stage then it would be much appreciated. Otherwise, I’ll update you all when we decide on our approach.

 

Thanks, wes

Hi Wes, Thanks for the summary, very useful to get a quick overview. Any updates on what sort of case design you ended up going with? And do you have any information about whether the 3D-printed case was ever used in the field?

Hello people,

 

I used two ziplocks during a 5-7 day sampling period in the Brazilian subtropical forest (Atlantic rain forest). During the sampling period there were heavy rain events but without prejudice to the AM. In some bags there was small condensation in the outer zip but there was no condensation in the inner bag.

 

 

I had two situations where some rodent gnawed the protections, but fortunately no rain occurred in the period and did not harm the AM. I believe it is important to take into consideration the fact that some mammal could take an interest in the material and destroy the protections.

 

 

 

New Posts
  • Hello all. For those who are looking for some inspiration: I found a cheap yet practical shock-/waterproof case. Available in three colours (beige, black orange) in the Geek/Wish store. With some minor adaptations it’s ideal for the AudioMoth. The inner lining consists of foam in which the shape of the AudioMoth can be easily cut out. For the fixation of the membrane I was inspired by the Aurita design and used a PVC shoulder washer. After drilling a hole just above the mic I enlarged it until the washer fits tightly. Since the materials (plastic vs PVC) are difficult to glue I used butyl tape to attach the shoulder washer. The membrane, standard cling film (10 micron), is mounted on top of the washer. In order to prevent damage by the sharp edges there there is an O-ring on top. The second O-ring stretches the membrane over the first one and provides extra protection against water ingress. I also provide a silicagel packet to prevent condensation on the membrane and as extra safety in case of the membrane is compromised. It is advised to check the membrane after each battery change because the cling film degrades due to weather conditions. Also the O-rings suffer from UV-degradation after a time so be sure to check their condition as well. The box has two ‘eyelets’, very convenient to attach the box. The box costs 2€ and together with the other stuff you have an excellent enclosure for less than 5€ and 15 minutes crafting.
  • Having recently got my v1.1 AM in GG round7, I'm really pleased to report that the recessed card and switch, means it fits really well in this case sized 85x58x33mm: https://www.ebay.co.uk/itm/Waterproof-Plastic-Electronic-Instrument-Project-Enclosure-Box-Case-US/253320952007 The width is a perfect snug fit, with small fillets of (camping mat) foam for the length in either end of lid, and also on the base. As was used in the recent British Bat Survey 2019 SW pilot (BBS19) I have used two layers of metal mesh treated with NicWax over the Mic- https://www.inoxia.co.uk/products/mesh/sheets/500-mesh Pros of this case: - Small sized, but has thick plastic making it strong. For example a bit smaller and much stronger than the OBO Bettermann Junction Box (A8 75x75x36mm ) used for the BBS19 survey, and also here . - A proper waterproof compressed rubber seal, mean this is very likely to be fully waterproof case - Not as cheap as the OBO A8, but at around £1.50 GBP its not expensive Cons: - Four small screens to lose in the field, and screwdriver to carry. - AMv1.1 only., It is too narrow for a AMv1.0 Overall I think I'll use these case for AM v1.1 in damp, or less secure situations. But if it is a dry and secure site I think I'll stick with the convenience of the OBO A8 case.
  • The guide (https://github.com/kitzeslab/opensoundscape) states that the enclosure must be "acoustically transparent over the mic". In this regard: 1. When using the provided bag, should we try to get the mic in contact with the plastic? 2. Are all "Ziploc baggies" made of the same material and are actually equivalent in terms of "sound transparency"? 3. Could anyone post which "Ziploc baggies" brands have been successfully used? 4. In general, are there tests on recording quality degradation using the different enclosure alternatives? Should we not have a consensus test of the type "recording an standard sound without any enclosure, with the standard enclosure and with the proposed enclosure"? Cheers! Agus
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