librosa.feature.spectral_bandwidth

librosa.feature.spectral_bandwidth(y=None, sr=22050, S=None, n_fft=2048, hop_length=512, win_length=None, window='hann', center=True, pad_mode='reflect', freq=None, centroid=None, norm=True, p=2)[source]

Compute p’th-order spectral bandwidth.

The spectral bandwidth [1] at frame t is computed by

(sum_k S[k, t] * (freq[k, t] - centroid[t])**p)**(1/p)
[1]Klapuri, A., & Davy, M. (Eds.). (2007). Signal processing methods for music transcription, chapter 5. Springer Science & Business Media.
Parameters:
y : np.ndarray [shape=(n,)] or None

audio time series

sr : number > 0 [scalar]

audio sampling rate of y

S : np.ndarray [shape=(d, t)] or None

(optional) 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.

win_length : int <= n_fft [scalar]

Each frame of audio is windowed by window(). The window will be of length win_length and then padded with zeros to match n_fft.

If unspecified, defaults to win_length = n_fft.

window : string, tuple, number, function, or np.ndarray [shape=(n_fft,)]
  • a window specification (string, tuple, or number); see scipy.signal.get_window
  • a window function, such as scipy.signal.hanning
  • a vector or array of length n_fft
center : boolean
  • If True, the signal y is padded so that frame t is centered at y[t * hop_length].
  • If False, then frame t begins at y[t * hop_length]
pad_mode : string

If center=True, the padding mode to use at the edges of the signal. By default, STFT uses reflection padding.

freq : None or np.ndarray [shape=(d,) or shape=(d, t)]

Center frequencies for spectrogram bins. If None, then FFT bin center frequencies are used. Otherwise, it can be a single array of d center frequencies, or a matrix of center frequencies as constructed by librosa.core.ifgram

centroid : None or np.ndarray [shape=(1, t)]

pre-computed centroid frequencies

norm : bool

Normalize per-frame spectral energy (sum to one)

p : float > 0

Power to raise deviation from spectral centroid.

Returns:
bandwidth : np.ndarray [shape=(1, t)]

frequency bandwidth for each frame

Examples

From time-series input

>>> y, sr = librosa.load(librosa.util.example_audio_file())
>>> spec_bw = librosa.feature.spectral_bandwidth(y=y, sr=sr)
>>> spec_bw
array([[ 3379.878,  1429.486, ...,  3235.214,  3080.148]])

From spectrogram input

>>> S, phase = librosa.magphase(librosa.stft(y=y))
>>> librosa.feature.spectral_bandwidth(S=S)
array([[ 3379.878,  1429.486, ...,  3235.214,  3080.148]])

Using variable bin center frequencies

>>> if_gram, D = librosa.ifgram(y)
>>> librosa.feature.spectral_bandwidth(S=np.abs(D), freq=if_gram)
array([[ 3380.011,  1429.11 , ...,  3235.22 ,  3080.148]])

Plot the result

>>> import matplotlib.pyplot as plt
>>> plt.figure()
>>> plt.subplot(2, 1, 1)
>>> plt.semilogy(spec_bw.T, label='Spectral bandwidth')
>>> plt.ylabel('Hz')
>>> plt.xticks([])
>>> plt.xlim([0, spec_bw.shape[-1]])
>>> plt.legend()
>>> plt.subplot(2, 1, 2)
>>> librosa.display.specshow(librosa.amplitude_to_db(S, ref=np.max),
...                          y_axis='log', x_axis='time')
>>> plt.title('log Power spectrogram')
>>> plt.tight_layout()
>>> plt.show()

(Source code)

../_images/librosa-feature-spectral_bandwidth-1.png