def _get_ta(f):
    """gets the factors for dba, invdba"""
    k1 = 2.242882e+16
    k3 = 1.562339
    p1 = 20.598997
    p2 = 107.65265
    p3 = 737.86223
    p4 = 12194.22
    ta1 = k3 * f ** 4 / ((f ** 2 + p2 ** 2) * (f ** 2 + p3 ** 2))
    ta2 = k1 * f ** 4 / ((f ** 2 + p1 ** 2) ** 2 * (f ** 2 + p4 ** 2) ** 2)
    return ta1, ta2
