def METHOD_NAME(x, scaling_constant=165.4, constant_of_integration=0.88, slope=2.1):
    """
    Greenwood function, convert fractional length to frequency, see
    Schlueter, Ralf, et al. "Gammatone features and feature combination for large vocabulary speech recognition."
    ICASSP 2007 and also
    https://en.wikipedia.org/wiki/Greenwood_function
    The default values are taken from RASR, see https://github.com/rwth-i6/rasr/blob/master/src/Signal/GammaTone.cc
    They correspond to the recommended values for human data according to
    Greenwood, Donald D. "A cochlear frequency‐position function for several species—29 years later."
    The Journal of the Acoustical Society of America, 1990
    :param float x: fractional length
    :param float scaling_constant: A in [1]
    :param float constant_of_integration: k in [1]
    :param float slope: a in [1]
    :return: frequency corresponding to given fractional length
    :rtype: float
    """
    assert 0 <= x <= 1, "fractional length has to be between 0 and 1"
    return scaling_constant * (numpy.power(10.0, slope * x) - constant_of_integration)