Conversation

Notices

1. Don Romano (alt) (thor@noagendasocial.com)'s status on Saturday, 13-Apr-2019 12:18:26 EDT Don Romano (alt)

   MEMS microphones are interesting. Flat frequency range and a PDM / sigma-delta output. I found one with an ultrasonic mode. It can be clocked up to 4.8 MHz. If you process the bitstream with a 96 kHz Lanczos filter and decimate it 25 times, you get a 192 kHz PCM signal. The upper frequency range of this microphone is 80 kHz. Ultrasonics is the only scenario I can think of where a 192 kHz sampling rate is actually useful and necessary. For music, a Nyquist rate of 40 kHz is more than sufficient.

   1. Don Romano (alt) (thor@noagendasocial.com)'s status on Saturday, 13-Apr-2019 12:22:18 EDT Don Romano (alt)

      in reply to

      I'm looking at digital MEMS microphones because they look like a cheap way of measuring absolute SPL levels at a wide range of audio frequencies. The gain is fixed at the factory and they give you the absolute dB SPL to dB FS curves in the datasheet. All you'd have to do is design an EQ curve with biquad filters to flatten the response and you'd have a fairly accurate meter.