Ultrasonic experiments illustrate Doppler and differential time-of-arrival measurement techniques

Two laboratory experiments based on 40 kHz ultrasonic signal measurements are described. The experiments illustrate techniques that are commonly applied to industrial applications. However, the lack of readily available hardware has limited their demonstration in the educational setting. The first experiment illustrates the Doppler effect as used in velocity measurement systems. The velocity of a moving ultrasonic source is computed from the frequency shift measured at the receiver. The second experiment illustrates differential time-of-flight measurements as used in navigational systems. The motion of a transmitter is computed from the differences in time-of-arrival at fixed receivers. The basic experiments are suitable for undergraduate labs. The signal analysis aspects of the experiments are appropriate for graduate-level digital signal processing courses