Abstract: To reduce the system complexity and the cost, the velocity sampling problem in the prediction of structural borne sound radiation was studied based on a baffled rectangular plate model. The factors affecting the choice of sampling interval were theoretically analyzed. It was found that the sampling interval is determined by the vibration mode at low frequency while the interval is determined by the vibration frequency at high frequency. The numerical results showed the critical frequency should satisfy such a rule that k_csinθ=const(k_c=2πF_c/c,F_c is the critical frequency, θ is the elevation angle of the observation point and c is the sound speed), and the applicability of this rule was validated by the numerical simulations and the experiment.