When in search of a low power wake on sound application we have the microphone for that application 2022-1001-1-ND. This piezo mems speaker operates at little to no power 10 μA of supply current (or 18 μW of power) until a certain threshold of voice or sound is reached and then can turn on within 200 μS. This offers something at a ultra low power and current state that is always listening for your application. They also are IP57 for more rugged applications. I have also attached some application notes and white papers that pertain to this.adding-wake-on-sound.pdf (1.1 MB) design-parameters-zeropower-listening.pdf (845.6 KB) using-vm1010-wake-on-sound-microphone.pdf (1.0 MB)