Erratum: mSOUND: An Open Source Toolbox for Modeling Acoustic Wave Propagation in Heterogeneous Media (IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control (2021) 68:5 (1476-1486) DOI: 10.1109/TUFFC.2021.3051729)

IN THE above article [1], the authors regret that there were some mistakes pertaining to (1)–(3) and (5). Equation (1) was expressed as: (Formula Presented). It should be instead written as in the following by adding an additional term to the right-hand side of the equation: (Formula Presented) where the frequency-independent absorption term γ δp/δt accounts for the absorption layer close to the computational boundary [2] and γ = γmax/ cosh² (γn) (γmax is a constant, α is a decay factor, and n denotes the distance in number of grid points from the boundary). The sound diffusivity δ in (1) was defined as δ = v(4/3 + μB/μ+(γ−1)/Pr ), where γ was the ratio of specific heats. To avoid confusion on γ, now the sound diffusivity is defined as γ= v(4/3+μB/μ+(γr −1)/Pr), where γr is the ratio of specific heats. Furthermore, (2) was expressed as (Formula Presented). It should be instead written as in the following by adding an absorption layer term on the RHS of the equation: (Formula Presented). Equations (3) and (5) are also missing the term related to the density variation of the medium. The revised equations are as follows: (Formula Presented). Finally, in the original article, page 1479, the word “medium” in the sentence “medium is also a structure containing spatially distributed speed of sound...” should be in the font dedicated to designate computer codes, i.e., medium.