Demo 11-07 Singing Pipes

Singing pipes are resonant acoustical open tubes that achieve their sound from the noise generated by convection currents. The first two metal tubes are excited directly by the flame from a torch. In the third tube, a glass tube, a flame is used to heat metal gauze in the tube. When the flame is removed, as in Figure 1, the convection currents created in the tube by the air heated by the hot gauze create a noise spectrum that leads to a sound resonance in the tube, as can be readily heard. When the tube is tipped to a horizontal orientation, no convection currents can flow so the tube does not sing