  It is shown that the velocity fluctuation spectra measured using a hot-wire
in the potential flow region of a turbulent jet near field in the presence of a
co-flow can be converted into the spectra of pressure fluctuations. The
proposed conversion method is based on the fact that the structure of
instability waves, which make a decisive contribution to the jet near-field
fluctuations, resembles homogeneous one-dimensional waves, which makes it
possible to locally link the pressure fluctuations and the fluctuations of the
streamwise velocity component measured by a hot-wire.
