Hi

I use the ADMP441 and I want to know how to compute the SPL value for a given digital output word. I know, that 120 dB SPL is mapped to the FS value of the ADC. Is the EIN value also mapped to the the value of the noise floor so that 33 dB SPL (EIN) is equivalent to the -87 dBFS word? Is the relationship between the SPL and the ADC word linear in this range? The data sheet and the application notes I read, couldn't answer this questions.

Thank you very much for any kind of help

You're correct; the relationship between input SPL and ADC output is linear. You can use the microphone's sensitivity to derive the SPL for any given output. On the ADMP441, the sensitivity is -26 dB FS, which means that will be the output level with a 94 dB SPL input.