  We discuss the structure, physical nature, dynamic genesis of clearly
detected diffuse backgrounds (radiations) in the Universe. From the point of
view of Wave Universe concept it is shown, that observed Backgrounds Hierarchy
(Polyphony of Universe) is close connected and causely determined by the sound
velocity Hierarchy of the physical medium, cosmic (polycomponent) plasma. The
well-known Microwave Background (Cosmic Background Radiation - CBR) corresponds
to the F[3] Background, that is characterized by the calculated sound velocity
C*[3]=11.483 km/s, by the calculated temperature T*[3]=2.9 grad.K and by
wavelength of the radiation intensity maximum lambda*[3]=1 mm.
