“Visualize sound frequencies spectrum with an OLED 128x32 display, Arduino Nano 33 BLE and an electret microphone amplifier (MAX9814).
See how a bar graph respond to music and sound in a little OLED display. Lowest frequencies toward the left end of the graph, highest frequencies toward the right.
Connections
Connect Mic GAIN depending the sensibility that better suits your system: VCC to mic GAIN for 40dB, low sensitivity, GND to mic GAIN for 50dB, medium sensitivity or let floating the mic GAIN for 60dB, high sensitivity.
Connect Analog pin 0 A0 to mic amp OUT
Connect 3.3V, GND, SDA (or analog 4 A4) and SCL (analog 5 A5) to I2C SSD1306
connect a 470 uF capacitor between VCC and GND in power bus
Getting low frequency noise?
The noise comes from any electric devices near your measuring system that are working. All of the electronic devices work with a fixed frequency and voltage of alternative current (AC) with the frequency of 50 Hz or 60 Hz is the power line frequency in your country. You can use a faraday cage to eliminate the noise easily. Put your circuit inside a box and connect the box to ground. Ground well the circuit.”