ABSTRACT
Following §II.5, we shall now study the most interesting case, when the source of ultrasonic waves oscillates harmonically with frequency ω. The velocity potential φ(x,t) can then be represented in the form φ(x,t)=Ψ(x)sin(ωt+β), https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9780429332227/64e5e3df-c95f-4a2a-a02e-98ef4c2d440f/content/equ3_1.tif"/>
