def _recspe(slow_spec, freqs, T):
    """
    Applied a correction factor to the spectrum of a slow-measured variable
    based on the response-time T

    Parameters
    -----------
    freqs: numpy.array
        frequencies
    slow_spec: numpy.array
        the spectrum
    T: float
        the response-time
    """
    import numpy as np
    assert len(slow_spec) == len(freqs)
    return slow_spec * (1.0 + 4.0 * np.pi ** 2.0 * freqs ** 2.0 * T ** 2.0)
