Fractal Feedback Reverb — User Guide
Chaotic reverberation: creates complex, evolving reverb tails using fractal delay patterns and modulated feedback for organic, non-linear spatial effects.
What this does
This script implements fractal feedback reverb — an advanced reverberation technique that creates complex, evolving spatial effects using fractal mathematics and chaotic feedback patterns. Generates reverb tails with self-similar delay structures, modulated feedback, and stereo variations that create organic, non-linear reverberation characteristics unlike traditional algorithmic reverbs.
Key Features:
- 4 Fractal Presets — From subtle spaces to extreme environments
- Fractal Delay Patterns — Self-similar delay time structures
- Modulated Feedback — Time-varying amplitude modulation
- Stereo Imaging — Independent left/right processing
- Memory Depth System — Controlled chaos through iteration memory
- Organic Evolution — Natural-sounding reverb decay
What is fractal feedback reverb? Traditional reverb: uniform decay, linear time response. Fractal reverb: creates complex, evolving reverberation with self-similar patterns across different time scales. Advantages: (1) Organic character: Natural-sounding space evolution. (2) Complex tails: Rich, detailed decay patterns. (3) Stereo width: Independent left/right processing creates immersive space. (4) Non-linear response: Unique reverb character for different inputs. (5) Controlled chaos: Mathematical structure within apparent randomness. Use cases: Experimental sound design, ambient music, cinematic scoring, spatial audio, acoustic simulation, creative effects.
Quick start
- Select Sound object in Praat
- Run
fractal_feedback_reverb.praat - Choose preset for pre-configured reverb characters
- Or adjust chaos_factor for fractal complexity
- Set tail_duration_seconds for reverb length
- Configure iterations for reverb density
- Click OK — fractal reverb applied
Quick tip: Start with Medium Fractal for balanced reverb character. Use Subtle Fractal for gentle spatial enhancement or Extreme Fractal for dramatic, evolving environments. Each processing creates unique reverb characteristics.
Processing Intensity: Higher iteration counts and longer tail durations significantly increase processing time. The script automatically handles stereo/mono conversion and creates appropriate reverb tails.
Fractal Theory
Fractal Delay Algorithm
🌀 Self-Similar Delay Structure
Core fractal delay calculation:
For each iteration i from 1 to iterations:
Primary delay calculation:
primary_delay = seed_delay × (chaos_factor ^ (i mod memory_depth))
Secondary delay:
secondary_delay = primary_delay / chaos_factor
Amplitude calculation:
amp1 = amplitude_base × (1 - i/iterations) × randomUniform(0.6, 1.4)
amp2 = amp1 × secondary_amplitude_factor
Feedback application:
Formula: "self + amp1 × self(x - primary_delay)"
Formula: "self + amp2 × self(x - secondary_delay) × cos(2×π×x×modulation_frequency)"
Key properties:
Self-similar patterns across time scales
Modulated feedback creates evolving character
Memory depth controls pattern repetition
Random variations ensure uniqueness
Stereo Processing System
🎧 Independent Channel Processing
Dual-channel fractal reverb:
For stereo sounds:
Extract left and right channels separately
Process each channel with slightly different parameters
Left channel:
primary_delay = seed_delay × (chaos_factor ^ (i mod memory_depth))
modulation_frequency = user setting (typically 30 Hz)
Right channel:
primary_delay = (seed_delay + 0.002) × ((chaos_factor + 0.02) ^ (i mod memory_depth))
modulation_frequency = 28 Hz (slightly different)
Benefits:
Natural stereo imaging
Avoids artificial "ping-pong" effects
Creates immersive, enveloping space
Each ear receives unique reverb character
For mono sounds:
Process single channel, then convert to stereo
Parameter Interactions
| Parameter | Function | Effect |
|---|---|---|
| chaos_factor | Fractal complexity | Higher = more dramatic delay variations |
| memory_depth | Pattern memory | Higher = longer pattern cycles, more structure |
| iterations | Reverb density | Higher = denser, more complex reverb tails |
| seed_delay | Initial delay | Sets starting point for fractal expansion |
| amplitude_base | Feedback level | Controls reverb intensity and decay time |
| modulation_frequency | Time variation | Higher = faster amplitude modulation |
Mathematical Foundation
Fractal properties:
Self-similarity: Patterns repeat at different scales
Scale factor: chaos_factor controls expansion/contraction
Memory system: i mod memory_depth creates cyclic patterns
Random variation: randomUniform ensures uniqueness
Feedback mathematics:
Each iteration: output = input + feedback × delayed_input
Amplitude decay: (1 - i/iterations) ensures natural fade
Modulation: cos(2π×x×frequency) creates time-varying character
Reverb characteristics:
Early reflections: Short delays from initial iterations
Late reverberation: Complex patterns from later iterations
Natural decay: Exponential amplitude reduction
Stereo spread: Parameter differences between channels
Reverb Presets
| Preset | Tail Duration | Iterations | Chaos Factor | Memory Depth | Character |
|---|---|---|---|---|---|
| Subtle Fractal | 1.5s | 20 | 1.5 | 3 | Gentle spatial enhancement |
| Medium Fractal | 2.0s | 32 | 1.8 | 4 | Balanced natural reverb |
| Heavy Fractal | 2.8s | 48 | 2.1 | 5 | Rich, complex environments |
| Extreme Fractal | 4.0s | 70 | 2.5 | 6 | Dramatic, evolving spaces |
🏛️ Spatial Character Applications
Subtle Fractal: Add gentle spatial presence to vocals and instruments without overwhelming the dry signal. Ideal for subtle enhancement in mixing.
Medium Fractal: Create natural-sounding room environments for most musical applications. Balanced between character and transparency.
Heavy Fractal: Generate rich, complex reverberation for sound design and ambient music. Creates distinctive spatial identities.
Extreme Fractal: Produce dramatic, evolving spaces for cinematic scoring and experimental music. Highly characterful and immersive.
Amplitude and Modulation Settings
Amplitude system:
amplitude_base (0.12-0.3):
Lower (0.12-0.18): Subtle, transparent reverb
Medium (0.18-0.24): Present, noticeable reverb
Higher (0.24-0.3): Prominent, forward reverb
secondary_amplitude_factor (0.65-0.95):
Lower (0.65-0.75): Focused reverb character
Medium (0.75-0.85): Balanced modulation
Higher (0.85-0.95): Rich, complex modulation
modulation_frequency (25-45 Hz):
Lower (25-30 Hz): Slow, evolving modulation
Medium (30-38 Hz): Natural time variation
Higher (38-45 Hz): Rapid, shimmering modulation
Random variation:
randomUniform(0.6, 1.4): ±40% amplitude variation
Ensures unique reverb character each processing
Prevents mechanical, repetitive patterns
Applications
Music Production
Vocal Processing: Use Subtle or Medium Fractal to add natural-sounding space to vocals without the artificial quality of many algorithmic reverbs. The fractal patterns create organic spatial enhancement.
Instrument Enhancement: Apply fractal reverb to acoustic instruments to create rich, complex spatial environments that enhance the natural character of the instrument rather than overwhelming it.
Sound Design
Environmental Design: Use Heavy or Extreme Fractal to create unique spatial identities for film, game, or installation sound design. The fractal patterns can simulate complex acoustic environments.
Textural Creation: Process synthetic or recorded sounds with extreme settings to create evolving textural beds and atmospheric pads for electronic and ambient music.
Experimental Audio
Spatial Composition: Use the fractal reverb as a compositional tool, creating spatial narratives that evolve throughout a piece. The self-similar patterns create coherent spatial development.
Acoustic Research: Study how fractal delay patterns affect spatial perception and reverb character. The controlled parameters allow systematic exploration of reverb perception.
Technical Considerations
Processing Time: High iteration counts (48+) with long tail durations can require significant processing time, especially for stereo files. The script provides visual feedback during processing.
Feedback Control: Very high amplitude_base values combined with many iterations can potentially cause excessive feedback or clipping. The script includes amplitude decay to prevent runaway feedback.
Stereo Imaging: The independent left/right processing creates natural stereo imaging without artificial "ping-pong" effects. For mono compatibility, the reverb remains coherent when summed to mono.