Further comments on the paper by Zinoviev and Bies, “On acoustic radiation by a rigid object in a fluid flow”

In this note, in response to the previous note by Zinoviev and Bies [Author's Reply to: F. Farassat, Comments on the paper by Zinoviev and Bies “On acoustic radiation by a rigid object in a fluid flow”, Journal of Sound and Vibration 281 (2005) 1224–1237], the present authors briefly discuss the assumptions used in the acoustic analogy and its intended applications. It is pointed out that the scattering problems discussed by Zinoviev and Bies do not fall within the intended applications of the Ffowcs Williams–Hawkings (FW–H) equation. However, the FW–H equation can be used to derive an integral equation for finding scattered pressure fields. We derive this integral equation and show the validity of the equation for some of the examples of Zinoviev and Bies. We respond to the other issues brought up by these authors in their notes. We believe that Zinoviev and Bies have misinterpreted the acoustic analogy and have not applied the Curle formula and the FW–H equation correctly.