Soon after a police station opened near his house, Christopher Cooper noticed a substantial increase in the amount of emergency vehicle traffic and their associated noises even though local officials had promised that it would not be disruptive. But rather than write down every occurrence to track the volume of disturbances, he came up with a connected audio-classifying device that can automatically note the time and type of sound for later analysis.

Categorizing each sound was done by leveraging Edge Impulse and an Arduino Nano 33 BLE Sense. After training a model and deploying it within a sketch, the Nano will continually listen for new noises through its onboard microphone, run an inference, and then output the label and confidence over UART serial. Reading this stream of data is an ESP32 Dev Kit, which displays every entry in a list on a useful GUI. The screen allows users to select rows, view more detailed information, and even modify the category if needed.

Going beyond the hardware aspect, Cooper’s project also includes a web server running on the ESP32 that can show the logs within a browser, and users can even connect an SD card to have automated file entries created. For more information about this project, you can read Cooper’s write-up here on Hackster.io.