While the default microphone mode on the Thingy52 is ADPCM - which I got working fine in my evaluation environment - the SPL mode defined in https://nordicsemiconductor.github.io/Nordic-Thingy52-FW/documentation/firmware_architecture.html#arch_sound is not clear to me. Does SPL stand for Sound Pressure Level? If so, can you provide more information regarding the implementation? I could not trace it in the firmware code in github.
Thanks,
Armin