def assembly_dyna_stif(omega_par, mass_matrix, damp_matrix, stif_matrix):
    """ Assembly the dynamic stiffness matrix.

    Args:
        omega_par (:obj:`float`): 2 pi frequency.
        mass_matrix (:obj:`numpy.array`): Mass matrix.
        damp_matrix (:obj:`numpy.array`): Damping matrix. 
        stif_matrix (:obj:`numpy.array`): Stiffness matrix.
    
    Returns:
        Dynamic stiffness matrix.
    """
    return -(omega_par**2) * mass_matrix + 1j * omega_par * damp_matrix + stif_matrix