Figs. 28 and 29 show the noise spectra measured in the 1451 and 1501 directions. The noise spectrum of the large
turbulence structures of the jet flow is plotted as the dotted curves in these figures . The entire spectrum consists of two
components. The main component is the large turbulence structures noise . At very low frequencies, below 100Hz , there is
an additional component.This component will be considered an unknown component for now.This unknown noise
component appears to show up first in Fig. 26, the noise spectrum in the 1351 direction. It spreads to lower frequencies as
the angle of radiation increases. The possible origin of this noise component will be discussed in a later section.