Expectant parents are thrilled to hear their unborn baby’s heartbeat, revealed by an ultrasonic motion detector. Suppose the fetus’s ventricular wall moves in simple harmonic motion with amplitude of 1.80 mm and a frequency of 115 per minute.
(a) Find the maximum linear speed of the heart wall. Suppose the motion detector in contact with the mother’s abdomen produces sound at 2 000 000.0 Hz, which travels through tissue at 1.50 km/s.
(b) Find the maximum frequency at which sound arrives at the wall of the baby’s heart.
(c) Find the maximum frequency at which reflected sound is received by the motion detector. By electronically “listening” for echoes at a frequency different from the broadcast frequency, the motion detector can produce beeps of audible sound in synchronization with the fetal heartbeat.