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A-weighting
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Log transform
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Harmonic-percussive-residual source separation. Especially for music.
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Per-channel energy normalization (PCEN). Static version exists as librosa.pen. Can also be learned as a neural network layer, see arXiv:1607.05666v1 Per-Channel Energy Normalization: Why and How.
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Whitening. Eg PCA. Removes redundancies in spectrogram. For each frame in spectogram
Normalization
- Cepstral Mean Normalisation (CMN): subtract the average feature value from each feature, so each feature has a mean value of 0. makes features robust to some linear filtering of the signal (channel variation).
- Cepstral Variance Normalisation (CVN): Divide feature vector by standard deviation of feature vectors, so each feature vector element has a variance of 1.
- For real-time, need to compute a moving average.
- RMS normalization
- Gaussianization, mapping to Gaussian distribution