Effect of turbulent boundary layer flow on measurement of acoustic pressure and intensity, revised

Acoustic measurements performed with pressure sensors (microphones and hydrophones) can be subject to misinterpretation if the sensors are in contact with a turbulent boundary layer flow. This misinterpretation is a result of non-propagating pressure fields (flow noise) generated by the turbulent motions of the fluid. In this paper, a simple analysis is given whereby the flow noise response of a pressure sensor placed in a turbulent boundary layer flow can be estimated. If the purpose of the sensor is to measure the sound emitted from an independent source outside of the turbulent boundary layer, then a bias for the measurement can be calculated. A bias formula for intensity measurements made with two-sensors under a turbulent boundary layer is also derived under the assumption of a very low Mach number flow.