Acoustic Evaluation of Three Turbo Propellers 830733

Three turbo-propellers were test flown on a Gulfstream Aerospace Commander 695 to measure their acoustic signatures in the near field, as measured by a wing mounted microphone, in the far field as recorded by a ground station in fly-over tests, and in the cabin as monitored by two microphones located in the cabin. Despite differences in airfoils, twist, and planform, the three-bladed propellers exhibited similar pressure-time traces in the near field; therefore, overall sound pressure levels are nearly equal for all propellers at consistent power and air speed. Several hundred acoustic signatures obtained from these propellers during the fly over tests and at pressure altitudes of 10,000 and 20,000 ft for cruise and full power and with both engines operating and with the right engine shut down have been digitized for ready access and are available to acousticians desiring this experimental data.