filter.py 文件源码

def _filter_attenuation(h, freq, gain):
    """Compute minimum attenuation at stop frequency"""
    from scipy.signal import freqz
    _, filt_resp = freqz(h.ravel(), worN=np.pi * freq)
    filt_resp = np.abs(filt_resp)  # use amplitude response
    filt_resp /= np.max(filt_resp)
    filt_resp[np.where(gain == 1)] = 0
    idx = np.argmax(filt_resp)
    att_db = -20 * np.log10(filt_resp[idx])
    att_freq = freq[idx]
    return att_db, att_freq