speech_prep::preprocessing::noise_reduction

Struct NoiseReducer

pub struct NoiseReducer { /* private fields */ }

Expand description

Noise reduction via spectral subtraction with adaptive noise profiling.

Implements the noise reduction specification:

STFT-based processing (25ms window, 10ms hop)
Adaptive noise profile estimation during VAD-detected silence
Magnitude-only spectral subtraction (preserves phase)
Achieves ≥6 dB SNR improvement target

§Performance

Target: <15ms per 500ms chunk (8000 samples @ 16kHz)
Expected: ~7ms (2x headroom)
Optimization: Precomputed FFT plans, reused buffers

§Example

use speech_prep::preprocessing::{NoiseReducer, NoiseReductionConfig, VadContext};

let config = NoiseReductionConfig::default();
let mut reducer = NoiseReducer::new(config)?;
let audio_stream = vec![vec![0.0; 8000], vec![0.05; 8080]];

// Process streaming chunks with VAD context
for chunk in audio_stream {
    let vad_ctx = VadContext { is_silence: detect_silence(&chunk) };
    let _denoised = reducer.reduce(&chunk, Some(vad_ctx))?;
}

Implementations§

Source §

impl NoiseReducer

Source

pub fn new(config: NoiseReductionConfig) -> Result<Self>

Create a new noise reducer.

§Arguments

config - Configuration parameters (window size, hop, α, β)

§Errors

Returns Error::Configuration if configuration is invalid.

§Example

use speech_prep::preprocessing::{NoiseReducer, NoiseReductionConfig};

let config = NoiseReductionConfig {
    oversubtraction_factor: 2.5, // Aggressive
    ..Default::default()
};
let reducer = NoiseReducer::new(config)?;

Source

pub fn reduce( &mut self, samples: &[f32], vad_context: Option<VadContext>, ) -> Result<Vec<f32>>

Apply noise reduction to audio samples.

§Arguments

samples - Input audio samples (typically 500ms chunk = 8000 samples @ 16kHz)
vad_context - Optional VAD state for noise profile updates

§Returns

Denoised audio with ≥6 dB SNR improvement on noisy input.

§Performance

Expected: ~7ms for 8000 samples (2x better than <15ms target)
Complexity: O(n log n) for FFT operations

§Example

use speech_prep::preprocessing::{NoiseReducer, NoiseReductionConfig, VadContext};

let mut reducer = NoiseReducer::new(NoiseReductionConfig::default())?;

// Chunk 1 (silence - initialize noise profile)
let chunk1 = vec![0.001; 8000];
let vad1 = VadContext { is_silence: true };
let output1 = reducer.reduce(&chunk1, Some(vad1))?;

// Chunk 2 (speech - apply noise reduction)
let chunk2 = vec![0.1; 8000];
let vad2 = VadContext { is_silence: false };
let output2 = reducer.reduce(&chunk2, Some(vad2))?;