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By extending the unied framework of Arakawa andKonor (2009), Dubos and Voitus (2014, hereafterDV14) describe the construction of a soundproofsemihydrostatic model.In this model, air parcels are constrained to remainclose to their hydrostatic height. Accuracy at non-hydrostatic scales is ensured by retaining vertical ac-celeration, approximated as the second Lagrangianderivative of hydrostatic height, in the vertical mo-mentum budget. The constraint imposed on the verticalpositionofairparcelsltersoutacousticwavesandgivesrise to a self-adjoint problem for a Lagrange multiplieridentiedasanonhydrostaticdisplacement—thatis,thedifference between the actual height of air parcels andtheir hydrostatic height.In the nal part of the paper, DV14 envisage an ap-plication of their model for data assimilation and ini-tialization purposes:Variational data assimilation systems may benet fromsuch an accurate elimination of acoustic waves, reducingthe optimization space. Similarly, it could be useful forinitialization purposes, avoiding the transient generationof acoustic waves from an initial ow. It may also behelpful to occasionally perform this projection while in-tegratingthefullycompressibleEulerequations,especiallyafter physical parameterizations have acted, potentiallytriggering the transient emission of acoustic waves.Recently, Benacchio et al. (2014,hereafterBOK14)andtherelatedworkbyKleinetal.(2014) andBenacchio(2014) proposed a blended semi-implicit soundproof–compressible model, motivating the development withreference to data assimilation and testing it in reducingtheamplitudeofacousticwavesgeneratedbyimbalancedinitial data. Discussing an extension of their work tolarger scales, BOK14 referred to unied approaches re-garding the correct limiting model for such an extension:Carefulconsiderationwillbeneededtoidentifythecorrectlarge-scalelimitingmodelinthelightofrecentsuggestionsof unied multiscale reduced models by Durran (2008),Arakawa and Konor (2009),andKonor (2014).The two excerpts reported above suggest the exis-tence of a connection between DV14 and BOK14. Thiscomment aims at clarifying this connection for thebenet of the readers of either paper.In BOK14, a pseudoincompressible formulation fea-turing the thermodynamic pressure was extended tocompressible dynamics byretrieving the time derivativeterm in the potential temperature equation written in

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