The sound card of a PC is used as a data acquisition system to study the characteristics of the propagation andreflection of sound pulses in open and closed cylindrical tubes of different lengths. From the analysis of the phases ofthe reflected pulses relative to the incident pulse it is possible to explore the difference between the reflection in openand closed ends. The physics that takes place at these points has important consequences in the interference conditionin mechanical and electromagnetic waves. From the transit times of the reflected pulses, the speed of sound in air caneasily be measured. The experiment is very low cost; it uses PVC drainage tubes, and a microphone and a speaker,each connected to a computers. The software used in the data acquisition is free shareware.