def nWaveRiseTime(pmax, patm=101e3, csnd=341, lamb=6.8e-8):
    """
    Calculate N-wave rise time

    Parameters
    ----------
    pmax -- N-wave overpressure amplitude in Pa
    patm -- atmospheric pressure in Pa
    csnd -- speed of sound in m/s
    lamb -- air molecular mean free path in m

    Returns
    -------
    trise -- N-wave rise time in s
    """
    trise = (lamb / csnd) * (patm / pmax)
    return trise