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  • Designing a waterproof casing with microphone

    Discussion in 'The main mechanical design forum' started by dennism, Jan 3, 2017.

    1. dennism

      dennism New Member

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      Hi, i was asked to make a casing for a pcb with a microphone. Problem is... i never made one before. I know how to do the casing, but the microphone-part is a mystery to me. My guess is... if the casing is watertight.. and if the microphone is inside the plastic, no sound will be recorded? Correct? Of maybe a thin layer? Lets say some holes of 0.3mm thickness? Would that let sound through.

      Is there anyone here with some experience on how to tackle this problem?
      Need some advice urgently :(
      thanks very much in advance
       
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    3. DanuteP

      DanuteP Member

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      Hi, if you need waterproof design with microphone, you should just use waterproof microphone on the PCB and ensure that there will be no leak around the microphone. Anyway the way you ask is hard to receive some decent answers, because you're not providing any information like how sensitive is the microphone, what's the size etc.
      I'm not good in accoustics and for form around microphone can't help, but for sure you shouldn't cover it.
       
    4. dennism

      dennism New Member

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      Hi thanks very much. I'm completely new to asking things regarding product design so i'm trying to find my way.. I will add this obvious things in the future. :) Thanks for helping me.

      The microphone used is this one
      http://www.puiaudio.com/pdf/TOM-1545P-R.pdf
      And when I say waterproofed, i mean ip55


      But why should the microphone itself be waterproofed, if the casing already is?
      Seems unnecessary to me? No water should enter inside the casing.

      Meanwhile i have found a pdf online regarding the design process of a waterproof cellphone http://www.paryleneengineering.com/_pdf/Waterproofcellphone.pdf
      See page 11
      Apperantly this document states that the mic. will only need to be covered by some sort of membrane or rubber and the sound will pass through.

      But i would like to know if someone can validate this. Or maybe point me in the direction of some best practices. Thanks!!!
       
      Last edited: Jan 6, 2017
    5. DanuteP

      DanuteP Member

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      Because if you use waterproof microphone you skip the step of thinking how to cover it (close it inside the case), without ruining the sound quality and makes the design of the case much easier. And you already asked if there should be an opening for the microphone which means that on that point your case will have a breach through microphone if you don't cover it.

      Yes covering with membrane will work.
      IP55 is pretty low class - water resistant, I wouldn't say waterproof in this case. There are ready waterproof microphone membranes on market, so just pick one.
       
    6. dennism

      dennism New Member

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      The microphone need to be outside the case, no? So there needs to a waterproofed hole in the casing to put the microphone outside?

      Could you point me into a direction?
       
    7. DanuteP

      DanuteP Member

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      Here IP classes are well explained https://www.cnet.com/how-to/water-dust-resistance-ratings-in-gadgets-explained/
      Actually it could work even without membrane, but if I was designing it I would prefer to cover it.

      I see that you can't understand what I mean with "microphone makes breach". I don't mean that your microphone is outside the case, when you have even 1 hole on your case (and you need one for the microphone) then inside this hole can enter water which will stop on the microphone and when your microphone is not covered and not water resistant, water will damage it, then product is broken and this means that you didn't make water resistant case no matter that only microphone is damaged. Is it more clear now what I mean?
       
    8. Gary Rose

      Gary Rose New Member

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      Hi,
      The simplest way to do this is to use an acoustic membrane from someone like Davidson or Goretex. Design your case as you would without the microphone then create a recess on the inside of the case for the microphone. Put a hole through the case to this recess and then fit an adhesive acoustic vent. You should probably consider some noise suppression component too. So get a silicone part to fit the recess and cradle the microphone body to prevent unwanted case noise.
       

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