@staticmethod
def _np_stft(data, fft_length, hop_length, window_length):
    frames = SpectralOpsTest._np_frame(data, window_length, hop_length)
    window = SpectralOpsTest._np_hann_periodic_window(window_length)
    return np.fft.rfft((frames * window), fft_length)
@staticmethod
def _np_stft(data, fft_length, hop_length, window_length):
    frames = SpectralOpsTest._np_frame(data, window_length, hop_length)
    window = SpectralOpsTest._np_hann_periodic_window(window_length)
    return np.fft.rfft((frames * window), fft_length)