We consider in dimension 3 a homogeneous superfluid at very low temperature T having two types of excitations, (i) gapless acoustic phonons with linear dispersion relation wave number, and (ii) gapped γ quasiparticles quadratic (massive) the vicinity its extrema. Recent works [Nicolis Penco (2018), Castin, Sinatra Kurkjian (2017, 2019)], extending historical study by Landau Khalatnikov on phono...