  Excitations in the form of quantized vortex rings are known to exist in
superfluid $^{4}He$ at energies and momenta exceeding those of the Landau
phonon-roton spectrum. They form a vortex branch of elementary excitations
spectrum which is disconnected from the Landau spectrum. Interference of vortex
ring excitations determines wake patterns due to uniformly traveling sources in
bulk superfluid at low speeds and pressures. The dispersion law of these
excitations resembles that of gravity waves on deep water with infrared wave
number cutoff. As a result, vortex wake patterns featuring elements of the
Kelvin ship wake are predicted. Specifically, at lowest speeds the pattern with
fully developed transverse and diverging wavefronts is present. At intermediate
speeds transverse wavefronts are absent within a cone whose opening angle
increases with the source velocity. At largest speeds only diverging wavefronts
confined within a cone whose opening angle decreases with the source velocity
are found. When experimentally observed, these changes in appearance of wake
patterns serve as indicators of the beginning part of the vortex branch of
elementary excitations.
