ABSTRACT
The propagation phenomenon considered in this note is the one governed by the acoustic equation in R 3: () ∂ 2 ∂ t 2 u ( x , t ) − Δ u ( x , t ) = 0 , https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003072096/6e6221c8-364d-4a5e-bfe5-98bb034e69b7/content/eq417.tif"/>
