ABSTRACT
Since first and second sound have different physical natures it is natural that they will be excited by different means. Let us consider some examples of the excitation of sound waves. We first look at the excitation of sound waves by a plane oscillating in a direction perpendicular to itself (which we choose as the x-axis). We may write the x-component of the velocity vs in the first and second type of excited sound waves in the form () v S 1 = A 1 exp { − i ω [ t − ( x / u ) ] } v S 2 = A 2 exp { − i ω [ t − ( x / u ) ] } https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429502897/20d72e0b-9d39-4175-acc6-a943547edf8a/content/eq325.tif"/>
