Sound sensor enclosure (MAX4466 / D1 mini)

Build an ambient sound sensor. This small box fits a microcontroller and the sensor, is powered from USB-C and looks neat on the wall.

My use-case: the sensor measures ambient sound levels in the room, and reports those to HomeAssistant. HA has a threshold rule - if sound reading is extremely high, then (seeing as the sensor is mounted next to building fire alarm) the fire alarm is probably active - send an alert.

Materials needed

1. Wemos D1 mini 4.0 USB C
2. MAX4466 sound sensor breakout board
3. M2 threaded inserts (OD 3…3.5mm depth max 3mm) x 4
4. M2 bolts x 4 (4…6mm)
5. USB C power
6. Double-sided tape for mounting

Build instructions

• Print both models. The enclosure body needs supports on the overhangs.
• Using a soldering iron, melt the 4x brass inserts into mounting holes for the D1 and MAX4466
• Solder 3x wire connections between the sensor and IC
• Assemble into the box
• Mount with tape

Software recommentation

1. Home Assistant
2. ESPHome
3. Firmware by Brenner Reubertt

Note on the firmware: if you get intermittent “WiFi auth failed” (WiFi credential is correct, it just won't connect), try increasing the update_interval of the ADC sound sensor reading - 10+ seconds worked for me. Theory: computation after the reading interferes with WiFi somehow.