Responses of a hot film and a pressure probe to acoustic excitation in mean flow

The responses of a hot film sensor and a pressure probe to acoustic excitation in steady flow up to a Mach number of 0.5 were measured and compared with the responses of a microphone, flush mounted in the wall of the flow duct. When compared in terms of fluctuating pressure, the response of the pressure probe was less than that of the wall microphone by about 2.1 dB or less at the 0.5 Mach number, while the response of the ho film probe was as much as 6.0 dB above that of the wall sensor, at the Mach numbers 0.3 and 0.5. In terms of fluctuating Reynolds number, the response of the hot film probe was greater than that of the wall-mounted sensor by at most 5.0 dB at the same Mach numbers. Removing the response contribution from fluctuating temperature in the hot film mathematical model improved the agreement between the two transducer responses for both comparisons.