Introduction

Voice-activated devices and noise-level monitors both need a way of turning sound into a number a microcontroller can react to, and that is exactly what this experiment demonstrates. A small electret microphone sound sensor module is wired to the STM32F070RB, and its amplified output is sampled rapidly to calculate a live sound intensity reading, printed continuously over UART.

2. Scope

This experiment covers understanding how an electret microphone module's onboard amplifier converts sound pressure into an analog voltage, and tracking a running peak-to-peak measurement rather than a single instantaneous sample, since audio signals fluctuate extremely rapidly. This extends single-sample ADC reading to a case where one sample is not representative, and a short window of samples must be aggregated first.

3. Prerequisite

3.1 Hardware

• STM32 Nucleo-F070RB development board

• Electret microphone sound sensor module, with onboard amplifier and analog output

• Breadboard and jumper wires

• Micro-USB cable

• PC with PuTTY

3.2 Software

• STM32CubeMX (standalone)

• STM32CubeIDE

• ST-LINK USB driver

• PuTTY, or an equivalent serial terminal application