When the volume of ambient sound reaches the set threshold, an interrupt is triggered.
The most important parts of the circuit are the microphone, an RMS-to-DC converter, two dual rail-to-rail Input/Output 10 MHz operational amplifiers, and a 12-bit digital-to-analog converter (DAC).
The 12-bit DAC provides the reference voltage — the noise threshold — for the comparator. You set the exact level through the SPI interface. The threshold should be configured through trial and error (4096 discrete values to select from).
Beside SPI, EN and OUT pins provide additional functionality.
The board works on a 3.3V power supply.