Sound Propagation, Reflection, and Its Relevance to Ultrasound Imaging
Abstract
The labs presented here build on a simple speed of sound activity and models medical ultrasound imaging by demonstrating how multiple reflections propagate in a closed system. A short sound pulse is emitted into a pipe that is closed at one end and contains one or more partially reflecting surfaces within the pipe. The variety of reflections and transmissions that occur can be measured with a microphone at the pipe entrance. We used white PVC pipes (4 m, schedule 40, 2-in diameter) and cut them into five pieces with lengths 0.4 m, 0.6 m, 0.8 m, 1 m, and 1.2 m (Fig. 1), cut to a precision of ±1.6 mm. We connected the pipes with couplings and modified some couplings to cause partial reflections, by covering 1⁄4, 1⁄2, or 3⁄4 of the coupling opening. For easiest adoption, use repair coupling rather than a standard coupling. If standard couplings are used we recommend boring them out so that the pipes can easily be connected and disconnected.