y'= u±yy u干Vs u+vy= 340+10 ×500(Hz)=547Hz u-Vs 340-20 340-10 V远 H-Yv= ×500(Hz)=458Hz u+Vs 40+20 νν s r vu vu m ± ′ = Hz547)Hz(500 20340 10340 sr =× −+ = −+ ν ′ = νvu vu 近 Hz458)Hz(500 20340 10340 sr =× +− = +− ν ′ = νvu vu 远