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gammatone(freq, ftype, order=None, numtaps=None, fs=None)

This function computes the coefficients of an FIR or IIR gammatone digital filter .

Parameters

freq : float: Center frequency of the filter (expressed in the same units as :None:None:`fs`).
ftype : {'fir', 'iir'}: The type of filter the function generates. If 'fir', the function will generate an Nth order FIR gammatone filter. If 'iir', the function will generate an 8th order digital IIR filter, modeled as as 4th order gammatone filter.
order : int, optional: The order of the filter. Only used when ftype='fir' . Default is 4 to model the human auditory system. Must be between 0 and 24.
numtaps : int, optional: Length of the filter. Only used when ftype='fir' . Default is fs*0.015 if :None:None:`fs` is greater than 1000, 15 if :None:None:`fs` is less than or equal to 1000.
fs : float, optional: The sampling frequency of the signal. :None:None:`freq` must be between 0 and fs/2 . Default is 2.

Raises

ValueError: If :None:None:`freq` is less than or equal to 0 or greater than or equal to fs/2 , if :None:None:`ftype` is not 'fir' or 'iir', if :None:None:`order` is less than or equal to 0 or greater than 24 when ftype='fir'

Returns

b, a : ndarray, ndarray: Numerator ( b ) and denominator ( a ) polynomials of the filter.

Gammatone filter design.

Examples

16-sample 4th order FIR Gammatone filter centered at 440 Hz

>>> from scipy import signal
... signal.gammatone(440, 'fir', numtaps=16, fs=16000)
(array([ 0.00000000e+00,  2.22196719e-07,  1.64942101e-06,  4.99298227e-06,
    1.01993969e-05,  1.63125770e-05,  2.14648940e-05,  2.29947263e-05,
    1.76776931e-05,  2.04980537e-06, -2.72062858e-05, -7.28455299e-05,
   -1.36651076e-04, -2.19066855e-04, -3.18905076e-04, -4.33156712e-04]),
   [1.0])

IIR Gammatone filter centered at 440 Hz

>>> from scipy import signal
... import matplotlib.pyplot as plt

>>> b, a = signal.gammatone(440, 'iir', fs=16000)
... w, h = signal.freqz(b, a)
... plt.plot(w / ((2 * np.pi) / 16000), 20 * np.log10(abs(h)))
... plt.xscale('log')
... plt.title('Gammatone filter frequency response')
... plt.xlabel('Frequency')
... plt.ylabel('Amplitude [dB]')
... plt.margins(0, 0.1)
... plt.grid(which='both', axis='both')
... plt.axvline(440, color='green') # cutoff frequency
... plt.show()

See :

Back References

The following pages refer to to this document either explicitly or contain code examples using this.

scipy.signal._filter_design.gammatone

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