ESP32 Audio Spectrum Analyzer

A real-time audio spectrum analyzer built on the ESP32, featuring a custom-designed PCB. Captures audio via an I2S MEMS microphone, runs FFT processing on-chip, displays a live 16-bar frequency spectrum on an OLED display, and streams real-time FFT data over WiFi to a browser-based visualizer via WebSockets.

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Demo Videos

Analyzer reacting to noise:

https://github.com/JadenS180/spectrum-analyzer/raw/main/media/spectrum-DemoNoise.MOV

Analyzer in a quiet environment:

https://github.com/JadenS180/spectrum-analyzer/raw/main/media/spectrum-DemoQuiet.MOV

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Web Dashboard

Reacting to noise

Quiet environment

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Photos

Full Breadboard Build

Side Views

Components

ESP32-WROOM-32 (front)	ESP32-WROOM-32 (back)
INMP441 Microphone (front)	INMP441 Microphone (back)
SSD1306 OLED (front)	SSD1306 OLED (back)

PCB

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Features

• Real-time FFT using 512-sample windows at 44,100 Hz
• 16 frequency bars mapped across the audible spectrum
• Hann windowing to reduce spectral leakage
• Peak hold indicators on each bar
• DC/low-frequency noise suppression via bin offset
• Custom 2-layer PCB designed in KiCad and manufactured by JLCPCB
• WiFi streaming via WebSockets to a browser-based canvas visualizer

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Hardware

Component	Description
ESP32-WROOM-32	Microcontroller
INMP441	I2S MEMS microphone
SSD1306	0.91" I2C OLED display (128x32)
AMS1117-3.3	3.3V LDO voltage regulator
USB-C Receptacle	Power input

Pin Mapping

Signal	ESP32 GPIO
I2S SCK	26
I2S WS	25
I2S SD	33
I2C SDA	21
I2C SCL	22

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Firmware

Written in Arduino C++ using the Espressif ESP32 package (v3.3.10).

Dependencies:

• arduinoFFT
• Adafruit SSD1306
• Adafruit GFX Library
• WebSockets
• ArduinoJson

To flash:

1. Open firmware/spectrum_analyzer.ino in Arduino IDE
2. Set your WiFi credentials in the firmware
3. Select board: ESP32 Dev Module under Espressif Systems
4. Connect ESP32 via USB and select the correct port
5. Upload

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Web Dashboard

The dashboard is a single HTML file in the dashboard/ directory. Open it in a browser while the ESP32 is powered and connected to WiFi. Update the WebSocket IP in index.html to match your ESP32's IP address.

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PCB Design

Designed in KiCad. The board is a 2-layer FR-4 PCB with a filled GND copper pour on F.Cu and a keep-out zone over the ESP32 antenna. Manufactured by JLCPCB.

KiCad schematic, PCB layout, and Gerber files are in the hardware/ directory.

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Repository Structure

spectrum-analyzer/
├── firmware/
│   └── spectrum_analyzer.ino
├── hardware/
│   ├── spectrum_analyzer.kicad_pro
│   ├── spectrum_analyzer.kicad_sch
│   ├── spectrum_analyzer.kicad_pcb
│   └── gerbers/
├── dashboard/
│   └── index.html
├── media/
│   ├── (photos)
│   └── (videos)
└── README.md

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Author

Jaden Smiles — github.com/JadenS180