Earlier studies [J. Acoust. Soc. Am. 29, 934 (1957)] of the mutual nonlinear interaction of two plane waves of sound with each other exhibited a singularity when the waves became collinear. The singularity is removed in this study, which leads to a method for calculating the pressure absorption coefficient α of a wave with wave vector k1resulting from interaction with isotropic acoustic waves having the energy density spectrumu(k). Thus, α= (4ρ0c20)−1(1+1/2Λ)2πFk10ku(k)dk+k1F∞d12u(k) idk+k21Fk11k−1u(k)dk], in which ρ0andc0represent the density and velocity of sound of the fluid which is assumed to be dispersionless. The constant 1/2Λ =ρ0cd0−1(dc/dρ)ρ0.Subject Classification: [43]25.22, [43]25.35.