Fundamentals of acoustics

Abstract

“Waves” are well-known to everybody, even when they are not cognitively identified as waves. While reading this book, light waves as an example of electromagnetic waves are scattered from the white paper and absorbed by printed letters. Electromagnetic waves were predicted by James Clerk Maxell’s theory in 1864 and experimentally discovered by Heinrich Hertz in 1888. Their spectrum from gamma radiation, X-rays, ultraviolet, the visible range, infrared toward spectra for technical communication systems offers a fascinatingly wide area of natural phenomena and technical applications. Waves are to be considered local oscillations in a physical “field” with the inherent effect of energy and information transport and are found in numerous areas of physics. The common approach in these areas is that small perturbations of the equilibrium yield linear or approximately linear forces and oscillating states of permanently recycled potential and kinetic energy.³

A row of dominos falling is an example where a kind of transport wave is observed without energetic equilibrium. Energy is not recycled. This effect is not a wave in the physical sense we discuss here!