There is evidence to show that the exhaust noise from gas turbines
contains components which exceed the jet mixing noise at low jet velocities.
This paper describes a theory developed to calculate the acoustic
power produced by temperature fluctuations from the combustor entering
the turbine. Using the turbine Mach numbers and flow directions at blade
mid-height, and taking a typical value for the fluctuation in temperature,
it has been possible to predict the acoustic power due to this mechanism
for three different engines. In all three cases the agreement with measurements
of acoustic power at low jet velocities is very good. Using a
measured spectrum of the temperature fluctuation the prediction of the
acoustic power spectrum agrees quite well with that measured
