I was wondering if anyone had experience with the commonly available ECM's? I want to sense very low frequencies like .1hz and I understand that the jfet inside the microphone leaks the charge away pretty fast. The spec sheets say 20 to 10,000 Hertz for example. Can I diddle that some way? Is there a part I have not yet found?
** Why not simply do a test on one ??
There ought to be some response at 0.1 Hz.
How about using a sealed speaker box with the mic placed inside and drive the speaker with very low frequencies. If you adjust the level to keep peak cone excursion constant, then pressure variations inside the box will be too.
.... Phil
A friend of mine skilled in such things says a exploding wire is pretty much a equal amplitude white noise source in the audio range. Evidently his test of choice for transducers is to pop a small diameter wire with a charged cap at a fair distance from the mic under test.
Steve Roberts
Many years ago I tested some cheap ones (partly from old cassette recorders) and they clearly showed the slow pressure changes from doors opening and closing in the house, or wind moving around the house. I did however need to close any vent holes in the back with a drop of glue.
-- Regards, Arie de Muynck
There used to be a burglar alarm based on exactly that. The mike was glued to a 100mtr coil of 0.5mm ID cheap plastic tube acting as a low pass filter. Sensitive enough to notice a floor deflecting in an upstair room.
Thank you, I think from what you said it is worth a try. I appreciate the input. Tony
Wow, That's sensitive. Thanks for the data. Tony
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