Macroscopic dynamics of superfluid <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>He</mml:mi><mml:mprescripts /><mml:none /><mml:mn>3</mml:mn></mml:mmultiscripts></mml:math> with a spatially modulated pair density wave

We discuss the macroscopic behavior of superfluid $^{3}\mathrm{He}$ phase (pair density wave phase) with a spatially modulated pair recently observed experimentally. As an order parameter we assume, based on experimental results and Landau-type model, variation function coupled to plane waves in perpendicular confinement. result find only one true Goldstone mode orbit space coupling aspects spatial modulations sample. This is predicted lead propagating sharing second sound acoustic arising from variations parameter. Due in-plane modulations, velocity first becomes anisotropic. In addition, velocities reflect static dynamic terms Fourth contrast, which also anisotropic, couples cross associated not any cross-coupling terms. Therefore measurements fourth could be used measure quite directly term. The situation studied here thus qualitatively different that suggested for supersolid $^{4}\mathrm{He}$ has solid broken translational symmetry as usual solid. spin obtain, neglecting tiny magnetic dipole interaction absence field, three pairs closely resembling planar distorted $B$ phase. Excitations presence and/or external field are investigated briefly.