I have a mems microphone with16 bits digital output and -26 dbFS of sensibility. I need to make a db meter. How convert this digital output to spl db ? Thank you for your video
Hello! Typically there has to be a calibration procedure, I think there could be different procedures and I'm not sure what is the best one for your specific product, but for example for Brüel & Kjær microphones you can use a B&K type 4231, it is a box which emits a specific frequency at a very specific pressure level (I think 1 kHz at 1 Pa), you insert the microphone inside, and then you can take note of what is the conversion. For B&K microphones you would look typically look at voltage rather than digtal values, but in an equivalent setup, if you get -10 dBFS at 1 Pa then you know that is the conversion, and from it you can convert anything else. You might also want to research the pistonphone calibration procedure
I've got several references to a threshold of pain (130 dB SPL) equating to 2.9 psi. However, when I convert 2.9 psi to Pa and get 19994 and I plug that in to the I(dB) equation 20*log10(19994/.0000203) where 20.3uPa is the reference threshold for hearing, I get 180 db. 63.24 Pa is 130 dB SPL, but that 63.24 Pa is 0.009172992 psi which is way off the 2.9 psi. What's going on?
Hello! The 130 dB threshold of pain is correct. However, this equals to 63.24 Pascal (per the 3nd formula at 6:33), and converting that to psi it gives 0.009137. 130 dB SPL for sure doesn't equal 2.9 psi.
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I have a mems microphone with16 bits digital output and -26 dbFS of sensibility.
I need to make a db meter.
How convert this digital output to spl db ?
Thank you for your video
Hello!
Typically there has to be a calibration procedure, I think there could be different procedures and I'm not sure what is the best one for your specific product, but for example for Brüel & Kjær microphones you can use a B&K type 4231, it is a box which emits a specific frequency at a very specific pressure level (I think 1 kHz at 1 Pa), you insert the microphone inside, and then you can take note of what is the conversion. For B&K microphones you would look typically look at voltage rather than digtal values, but in an equivalent setup, if you get -10 dBFS at 1 Pa then you know that is the conversion, and from it you can convert anything else.
You might also want to research the pistonphone calibration procedure
I've got several references to a threshold of pain (130 dB SPL) equating to 2.9 psi. However, when I convert 2.9 psi to Pa and get 19994 and I plug that in to the I(dB) equation 20*log10(19994/.0000203) where 20.3uPa is the reference threshold for hearing, I get 180 db. 63.24 Pa is 130 dB SPL, but that 63.24 Pa is 0.009172992 psi which is way off the 2.9 psi. What's going on?
Hello! The 130 dB threshold of pain is correct. However, this equals to 63.24 Pascal (per the 3nd formula at 6:33), and converting that to psi it gives 0.009137. 130 dB SPL for sure doesn't equal 2.9 psi.