9-7 Vibrating system and sources of sound We have already studied the propagation of the sound wave, and now to understand the nature of the sound we must study the vibration system that produces it Ne can classify musical instruments into three categories: those based on vibration string; those based on vibration column of air and more complex system including plates, rods, and membranes (aThe vibrating system has a large number ofWe have already studied the propagation of the sound wave, and now to understand the nature of the sound we must study the vibration system that produces it. We can classify musical instruments into three categories: those based on vibration string; those based on vibration column of air, and more complex system including plates, rods, and membranes. (a)The vibrating system has a large number of 19-7* Vibrating system and sources of sound