Open Source Digital Audio Processing

AudioNoise

Real-Time Audio Effects Framework

AudioNoise is an open-source digital audio effects framework created by Linus Torvalds, the founder of Linux. Built for real-time processing with sub-millisecond latency, AudioNoise implements classic guitar pedal effects including phaser, flanger, echo, and FM synthesis using efficient IIR filters and delay lines.

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Audio Effects

Classic guitar pedal effects implemented with single-sample, zero-latency processing for real-time audio chains.

Phaser

All-pass filter based phaser effect that emulates analog RC network circuits. Creates the classic sweeping, swirling sound characteristic of vintage phasers.

Flanger

Delay-based flanging effect with modulated delay time. Produces the characteristic jet-plane swoosh through comb filtering.

Echo

Digital delay loop implementation supporting delays up to 1.25 seconds. Linear interpolation for smooth delay time changes.

FM Synthesis

Frequency modulation implementation for creating complex timbres and textures beyond traditional analog effects.

Biquad Filters

Second-order IIR filters supporting low-pass, high-pass, band-pass, notch, and all-pass configurations with Direct Form 2 processing.

Visualization

Python-based waveform visualizer with interactive zoom, pan, and sample inspection. Built for analyzing effect output in real-time.

Technical Specifications

Designed for professional-grade audio processing with minimal resource usage.

48kHz
Sample Rate
<1ms
Processing Latency
32-bit
Sample Depth
GPLv2
Open Source License

About the Project

Learning Digital Audio Processing

AudioNoise began as a software companion to a hardware guitar pedal project built around the RP2354 microcontroller and TAC5112 audio codec. The hardware achieved sub-millisecond ADC-to-DAC latency, inspiring this purely digital exploration.

The project focuses on fundamental DSP concepts: IIR filters, delay lines, and basic modulation. Every effect follows a "single sample in, single sample out" design philosophy, ensuring zero added latency for real-time audio chains.

This is intentionally a learning project rather than a production-ready effects suite. The implementations prioritize clarity and educational value over sophisticated features like FFT-based processing or cabinet emulation.

LT

Linus Torvalds

Creator of Linux and Git

"The main design goal has been to learn about digital audio processing basics. Exactly like the guitar pedal was about learning about the hardware side. So no fancy FFT-based vocoders or anything like that, just IIR filters and basic delay loops."

Getting Started

Clone the repository and start experimenting with digital audio effects.

1

Clone the Repository

Get the source code from GitHub.

git clone https://github.com/torvalds/AudioNoise.git
2

Install Dependencies

Ensure you have the required tools: gcc, ffmpeg, aplay (ALSA), and Python with numpy/matplotlib.

sudo apt install gcc ffmpeg alsa-utils python3-numpy python3-matplotlib
3

Build and Run

Use the Makefile to build the project and process audio samples.

make