I need to detect very low amplitude sound in air (typically 0dB), in an enclosed space of less than 100 cubic centimeters, in the low ultrasonic region ie 20kHz to maybe 50kHz. I will be narrow bandpass filtering it in any case. The frequency is fixed. Temperature range 0degC to about 90degC. What microphone type is most suitable?
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10 dB relative to what? – Andy aka Feb 08 '19 at 10:32
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@Andyaka https://en.wikipedia.org/wiki/Sound_pressure – Dirk Bruere Feb 08 '19 at 10:38
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You will be noise-limited with this one, so it will depend on what you mean when you say "detect". If you know the frequency content of the sound you are looking for, you can use narrowband techniques to detect it. – sh- Feb 08 '19 at 11:53
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@sh- modified question – Dirk Bruere Feb 08 '19 at 11:58
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3@DirkBruere so, dB_SPL? – Marcus Müller Feb 08 '19 at 12:04
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2Given that you have a small space, you might best try to use a MEMS capsule that supports the frequency and temperature range. Knowles SPU0410LR5H-QB appears to be a candidate. Its noise properties however will mean that you need a narrow bandpass to see the signal. FFT and/or lock-in techniques may help. – sh- Feb 08 '19 at 12:42
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1Does noise-limited mean air-molecule-bouncing-around limited? – analogsystemsrf Feb 08 '19 at 13:30
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@MarcusMüller Yes. 0 dBspl – Dirk Bruere Feb 08 '19 at 13:38
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1My understanding is that ribbon microphones are among the most sensitive you can get, but they're also large, expensive, and are easily destroyed by overly loud sounds. – Hearth Feb 08 '19 at 15:41
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@Hearth I am size constrained quite severely. Maybe an active surface exposed to the sound of less than 4 cm^2 – Dirk Bruere Feb 08 '19 at 16:13