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Audio Effects

Audio effects transform audio in real-time to improve sound quality or add character.

What Are Audio Effects?​

Effects are signal processors that modify audio as it passes through. VoxaTrace provides three essential vocal effects:

EffectWhat It DoesWhen to Use
Noise GateMutes audio below a thresholdRemove background noise
CompressorReduces dynamic rangeEven out volume differences
ReverbAdds room ambianceMake vocals sound richer

Signal Flow​

Effects are applied in a specific order (called a "chain"):

Microphone Input
       ↓
  [Noise Gate]  ← Removes noise when not singing
       ↓
  [Compressor]  ← Evens out loud and soft parts
       ↓
    [Reverb]    ← Adds space and ambiance
       ↓
  Speaker Output

The order matters! A different order produces different results.

Understanding Each Effect​

Noise Gate​

A noise gate mutes audio when it falls below a threshold. Think of it as an automatic mute button.

Audio Level:    ████░░████████░░░░░░████████░░░░░░░░░░░░░░
Threshold:      ────────────────────────────────────────── (-40 dB)
Gate Output:    ████░░████████░░░░░░████████░░░░░░░░░░░░░░
                 ↑     ↑           ↑          ↑
              Opens  Open      Opens      Closed (muted)

Use it to:

  • Remove background noise during pauses
  • Clean up breath sounds between phrases
  • Eliminate hum when not singing

Key parameters:

  • Threshold (dB): Below this level, audio is muted. -40 dB is typical.
  • Hold Time (ms): How long to stay open after audio drops below threshold.
  • Attack/Release (ms): How quickly the gate opens/closes.

Compressor​

A compressor reduces the difference between loud and soft sounds. It makes quiet parts louder and loud parts quieter.

Input:         ░░██░░░░░░░░████████████░░░░░░░░░░███░░░░░
                 ↑          ↑                    ↑
               Quiet      Loud                 Quiet

Output:        ███████░░░░░████████░░░░░░░░░░░░██████░░░░
                 ↑          ↑                    ↑
               Boosted   Reduced              Boosted

Use it to:

  • Keep vocals at consistent volume
  • Prevent clipping on loud notes
  • Make softer passages audible

Key parameters:

  • Threshold (dB): Compression starts above this level.
  • Ratio: How much to reduce (4:1 means 4 dB input = 1 dB output above threshold).
  • Attack (ms): How quickly compression kicks in.
  • Release (ms): How quickly compression releases.

Reverb​

Reverb simulates the acoustic reflections of a room. It makes audio sound like it's in a physical space.

Dry Signal:    ████░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░
                ↓
Reverb Added:  ████████████░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░
                   ↑
              Decay/tail

Use it to:

  • Add warmth and depth to vocals
  • Make recordings sound less "dry" or clinical
  • Create ambiance matching your app's style

Key parameters:

  • Mix: Blend of dry (original) and wet (reverb) signal. 0.0 = dry, 1.0 = all reverb.
  • Room Size: How big the virtual room is. Larger = longer decay.

Using CalibraEffects​

Basic Usage​

// Create with preset
val effects = CalibraEffects.create(EffectsPreset.VOCAL_CHAIN)

// Process audio (in-place)
effects.process(samples)

// Cleanup
effects.release()

Presets​

// Full vocal chain: gate + compressor + reverb
val effects = CalibraEffects.create(EffectsPreset.VOCAL_CHAIN)

// Minimal processing for practice/learning
val effects = CalibraEffects.create(EffectsPreset.PRACTICE)

// Voice recording: gate + light compression
val effects = CalibraEffects.create(EffectsPreset.VOICE)

Custom Chain​

Build exactly what you need using the Config Builder pattern (ADR-001 compliant):

val config = CalibraEffectsConfig.Builder()
    .addNoiseGate(NoiseGatePreset.LIGHT)         // Light gating
    .addCompressor(CompressorPreset.VOCALS)       // Vocal compression
    .addReverb(mix = 0.2f, roomSize = 0.4f)      // Subtle reverb
    .build()  // Returns CalibraEffectsConfig

val effects = CalibraEffects.create(config)

Or omit effects you don't need:

// Reverb only
val config = CalibraEffectsConfig.Builder()
    .addReverb(ReverbPreset.SMALL_ROOM)
    .build()
val effects = CalibraEffects.create(config)

// Gate and compressor only (no reverb)
val config = CalibraEffectsConfig.Builder()
    .addNoiseGate()
    .addCompressor()
    .build()
val effects = CalibraEffects.create(config)

Runtime Adjustment​

Tweak parameters during playback:

// User moves reverb slider
reverbSlider.onValueChanged { value ->
    effects.setReverbMix(value)  // 0.0 to 1.0
}

// User adjusts noise gate
gateSlider.onValueChanged { value ->
    effects.setNoiseGateThreshold(value)  // -60 to 0 dB
}

// User adjusts compression
compressionSlider.onValueChanged { value ->
    effects.setCompressorThreshold(value)  // -40 to 0 dB
}

Integration with Recording​

Process audio during recording:

val effects = CalibraEffects.create(EffectsPreset.VOCAL_CHAIN)

recorder.audioBuffers.collect { buffer ->
    val samples = buffer.toFloatArray()

    // Process in-place
    effects.process(samples)

    // Now samples has effects applied
    // Use for playback monitoring or save to file
}

effects.release()

Integration with Playback​

Use player's processing tap:

val effects = CalibraEffects.create(EffectsPreset.VOCAL_CHAIN)

// Install tap on player
player.setProcessingTap { samples ->
    effects.process(samples)
}

player.play()

// Later...
player.setProcessingTap(null)  // Remove tap
effects.release()

Performance Considerations​

EffectCPU CostNotes
Noise GateVery LowSimple threshold comparison
CompressorLowEnvelope following
ReverbModerateMultiple delay lines

Tips:

  • Use presets when possible (optimized configurations)
  • Disable unused effects (don't add what you won't use)
  • Process at 16kHz when possible (less samples to process)

Common Configurations​

Karaoke App​

// Rich reverb for karaoke feel
val config = CalibraEffectsConfig.Builder()
    .addNoiseGate(NoiseGatePreset.STANDARD)
    .addCompressor(CompressorPreset.VOCALS)
    .addReverb(mix = 0.35f, roomSize = 0.6f)  // More reverb
    .build()
val effects = CalibraEffects.create(config)

Practice/Learning App​

// Minimal processing - hear your real voice
val config = CalibraEffectsConfig.Builder()
    .addNoiseGate(NoiseGatePreset.LIGHT)  // Just reduce noise
    .build()
val effects = CalibraEffects.create(config)

Voice Recording​

// Clean, professional sound
val config = CalibraEffectsConfig.Builder()
    .addNoiseGate(NoiseGatePreset.STANDARD)
    .addCompressor(CompressorPreset.VOCALS)
    .addReverb(mix = 0.1f, roomSize = 0.3f)  // Subtle room
    .build()
val effects = CalibraEffects.create(config)

Podcast Style​

// Consistent volume, no reverb
val config = CalibraEffectsConfig.Builder()
    .addNoiseGate(NoiseGatePreset.AGGRESSIVE)
    .addCompressor(CompressorPreset.VOCALS)  // Heavy compression
    .build()
val effects = CalibraEffects.create(config)

Troubleshooting​

"Audio sounds choppy"​

The noise gate may be cutting off the start of words. Try:

  • Lowering threshold (setNoiseGateThreshold(-50f))
  • Increasing hold time

"Volume jumps around"​

The compressor settings may be too aggressive. Try:

  • Lower ratio (2:1 instead of 8:1)
  • Longer attack time
  • Longer release time

"Too much echo"​

Reduce reverb mix:

effects.setReverbMix(0.1f)  // Start low, increase gradually

"Vocals sound harsh"​

The compressor may be squashing too hard:

  • Raise threshold
  • Use CompressorPreset.GENTLE

Next Steps​