[填空题]
If the velocity of blood flow in th6covsbu ,d3t *e aorta is normally a5r 86 luoz jspaq-ml v25tjh01bout 0.32 m/s what beat frequency would you expect if 5.50-MHz ultrasound waves were direct 8r6vjs52h0l-z p jtmua1qo 5led along the flow and reflected from the red blood cells? Assume that the waves travel with a speed of $1.54 \times10^{3 }$ m/s $ \times10^{3 }$Hz
