Tutorial on vibration and sound

Abstract

Over the years I have written many tutorials on vibroacoustics. This tutorial summarizes much of the material in those articles, starting with structural flexural vibrations and how they radiate sound. I explain structural modes of vibration, how they sum into structural mobilities, and how to use infinite plate theory to estimate the means of those mobilities. I also show that as structural damping increases, the mobilities of finite structures converge to that of an infinite structure. Next, you will see how structural flexural waves radiate sound into adjacent acoustic spaces. The radiated sound power may be normalized to a nondimensional radiation efficiency. Next we will examine fluid loading effects on structures, including loading from exterior and internal acoustic regions. I will show how exterior heavy fluid loading (from water) significantly mass loads and radiation damps structural vibrations. I will also show how internal air cavities can stiffen low order structural modes, and in some cases cause coupled oscillator behavior when structural and cavity mode resonance frequencies coincide. Finally, I will explore the fundamentals of sound transmission loss through structural barriers. My complete tutorial series on vibroacoustics is available at hambricacoustics.com.