spectrogram.py 文件源码

def logscale_spec(spec, sr=44100, factor=20.):
    """ scale frequency axis logarithmically """
    timebins, freqbins = np.shape(spec)
    scale = np.linspace(0, 1, freqbins) ** factor
    scale *= (freqbins - 1) / max(scale)
    scale = np.unique(np.round(scale))

    # create spectrogram with new freq bins
    newspec = np.complex128(np.zeros([timebins, len(scale)]))
    for i in range(0, len(scale)):
        if i == len(scale) - 1:
            newspec[:, i] = np.sum(spec[:, scale[i]:], axis=1)
        else:
            newspec[:, i] = np.sum(spec[:, scale[i]:scale[i + 1]], axis=1)

    # list center freq of bins
    allfreqs = np.abs(np.fft.fftfreq(freqbins * 2 - 1, 1. / sr)[:freqbins + 1])
    freqs = []
    for i in range(0, len(scale)):
        if i == len(scale) - 1:
            freqs += [np.mean(allfreqs[scale[i]:])]
        else:
            freqs += [np.mean(allfreqs[scale[i]:scale[i + 1]])]
    return newspec, freqs