Traditional experiments measuring the speed of sound consist of studying harmonics by changing the
length of a glass tube closed at one end. In these experiments, the sound source and observer are
outside of the tube. In this paper, we propose the modification of this old experiment by studying
destructive interference in a pipe using a headset, iPhone and iPad. The iPhone is used as an
emitter with signal generator application and the iPad is used as the receiver with a spectrogram
application. Two experiments are carried out for measures: the emitter inside of the tube with the
receiver outside, and vice versa. We conclude that it is even possible to adequately and easily
measure the speed of sound using a cup or a can of coke with the method described in this paper.