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Microphone in a bubble...

Posted: Wed Nov 07, 2018 12:56 pm
by Externet
Hi.
What material would be less detrimental to fidelity for an electret microphone enclosed behind/inside a waterproof, corrosion proof membrane ?
A rigid bubble, a flexible bubble, a silicone, a plastic, a metal, a cellophane, a rubber, a deflated bubble, an inflated one... ?

Re: Microphone in a bubble...

Posted: Wed Nov 07, 2018 3:12 pm
by dyarker
Not a truely rigid bubble. Sound (higher and lower preasure) on the outside needs to deform/flex to make higher and lower presure in the air inside.

Same for "Gummy Bear" soft, except sound is absorbed, nothing inside to vibrate the mic element.

Re: Microphone in a bubble...

Posted: Thu Nov 08, 2018 11:17 am
by haklesup
All of those materials would impede sound waves and attenuate the sound somewhere along the spectrum. Even considering an idealized flexible membrane, you now have 2 air masses coupling through the membrane with one being much much smaller than the other. Since air on both sides is compressible, no membrane is ideal and other factors such as temperature may vary, this should not be a high fidelity setup.

On the other hand, any of those setups could make an interesting guitar effects pickup or unique voice distortion for a musician. Filling the inner volume with more or less dense than air gasses would be interesting too. Most Distortion is done electronically now however AFAIK

Re: Microphone in a bubble...

Posted: Thu Nov 08, 2018 12:33 pm
by dyarker
Oh yeah! How waterproof? Rain/spit/sweat? Or, submerged? (and depth?)

Re: Microphone in a bubble...

Posted: Fri Nov 09, 2018 11:52 am
by haklesup
an electret mic is not the highest fidelity options on todays market anyway. Its handy because it can be used with Voltage boas rather than current bias. Most of these could probably be waterproofed by simply putting tape over the sound port and sealing the electrical contacts in epoxy. They may already be somewhat weather resistant because I think you can just shake out the water and air dry the case, the sensor is already a sealed membrane construction. (image search "electret mic construction")

Re: Microphone in a bubble...

Posted: Fri Nov 09, 2018 6:08 pm
by Lenp
Do I see into the future, a Sulfur hexafluoride and Helium gas mixing system, putting gasses into a acoustic chamber for the next generation of guitar adulteration?

Re: Microphone in a bubble...

Posted: Sat Nov 10, 2018 7:10 am
by Externet
haklesup wrote:
Fri Nov 09, 2018 11:52 am
an electret mic is not the highest fidelity options on todays market anyway. Its handy because it can be used with Voltage boas rather than current bias. Most of these could probably be waterproofed by simply putting tape over the sound port and sealing the electrical contacts in epoxy. They may already be somewhat weather resistant because I think you can just shake out the water and air dry the case, the sensor is already a sealed membrane construction. (image search "electret mic construction")
Thanks, haklesup.
The "fidelity" word included in the original materials search post as to avoid introducing distortion from a proper material wrapping/encapsulating. For voice-only use range, does not need 'high fidelity'
Tape waterproofing does not work, muffles it, and as the type of microphone is vented in the back and electrets are very corrosion-prone. Shaking it dry is not applicable; as soon as corrosive liquids are present, its life days are counting, fast.
- No guitar adulteration applications :smile:
Exploring a sealed wrap forming a rigid/thin bubble with thin cellophane (as cigarette pack wrapper) to pass vibrations... I bought silicone condoms too for testing :shock:
Latex water balloons smell like too resilient material, and degrade. tested iffy.
Evaluating/comparing more materials is next...



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Re: Microphone in a bubble...

Posted: Sun Nov 11, 2018 9:22 am
by evahle
Myself, I'd setup a test station with the microphone to be tested, and an amp capable of 20-20khz output to a scope.
The mic would be setup to accept the material to be tested, and easily changed to any material I'd want to test it with.
Then I'd have a sound sweep generator with speaker in front of the mic.
I'd then chart the results on a spreadsheet, with the type of material tested, as well as the frequency response.