librosa.feature.spectral_flatness¶

librosa.feature.spectral_flatness(y=None, S=None, n_fft=2048, hop_length=512, amin=1e-10, power=2.0)[source]¶

Compute spectral flatness

Spectral flatness (or tonality coefficient) is a measure to quantify how much noise-like a sound is, as opposed to being tone-like [1]. A high spectral flatness (closer to 1.0) indicates the spectrum is similar to white noise. It is often converted to decibel.

[1]	Dubnov, Shlomo “Generalization of spectral flatness measure for non-gaussian linear processes” IEEE Signal Processing Letters, 2004, Vol. 11.

Parameters:

y : np.ndarray [shape=(n,)] or None: audio time series
S : np.ndarray [shape=(d, t)] or None: (optional) pre-computed spectrogram magnitude
n_fft : int > 0 [scalar]: FFT window size
hop_length : int > 0 [scalar]: hop length for STFT. See librosa.core.stft for details.
amin : float > 0 [scalar]: minimum threshold for S (=added noise floor for numerical stability)
power : float > 0 [scalar]: Exponent for the magnitude spectrogram. e.g., 1 for energy, 2 for power, etc. Power spectrogram is usually used for computing spectral flatness.

Returns:

flatness : np.ndarray [shape=(1, t)]: spectral flatness for each frame. The returned value is in [0, 1] and often converted to dB scale.

Examples

From time-series input

>>> y, sr = librosa.load(librosa.util.example_audio_file())
>>> flatness = librosa.feature.spectral_flatness(y=y)
>>> flatness
array([[  1.00000e+00,   5.82299e-03,   5.64624e-04, ...,   9.99063e-01,
      1.00000e+00,   1.00000e+00]], dtype=float32)

From spectrogram input

>>> S, phase = librosa.magphase(librosa.stft(y))
>>> librosa.feature.spectral_flatness(S=S)
array([[  1.00000e+00,   5.82299e-03,   5.64624e-04, ...,   9.99063e-01,
      1.00000e+00,   1.00000e+00]], dtype=float32)

From power spectrogram input

>>> S, phase = librosa.magphase(librosa.stft(y))
>>> S_power = S ** 2
>>> librosa.feature.spectral_flatness(S=S_power, power=1.0)
array([[  1.00000e+00,   5.82299e-03,   5.64624e-04, ...,   9.99063e-01,
      1.00000e+00,   1.00000e+00]], dtype=float32)