1. Ultrasound is sound waves with frequencies higher than the upper audible limit for human hearing. Bats use ultrasound to for locating prey and obstacles. Ultrasonic devices are also used to detect objects, measure distances and have many important medical applications. One such application is to monitor fetal heartbeats by reflecting ultrasound waves off the fetus in the womb. In this problem we will explore the ideas of doppler shift and beat frequency to understand how ultrasound is used to monitor fetal heart health.