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Acoustic vector sensors (AVS), as they were recently developed based upon acoustic particle velocity sensors may improve the performance of Unmanned Aerial Vehicles (UAV) in terms of automatic take off and landing (ATOL), ground surveillance and mid air anti collision.

The NVH optimization process of a power train often consists in a target setting for the acoustic power radiation of the engine in free field working conditions (in an anechoic or semi-anechoic room). This method requires the engine to be dismounted from the car and to be measured in an anechoic or semi-anechoic room which is costly and time consuming. Moreover the free-field characterization is not a good predictor of the acoustic behavior of the power train when it is mounted in the engine bay of a car (very reactive field). This paper presents a number of existing methods to determine the acoustic power radiation pattern of the engine mounted in a car using an intensity probe which is based on a pressure sensor and a particle velocity sensor. For the lower frequencies the velocity probe is used, for the higher frequencies both pressure and velocity is used to measure intensity. A new method for the mid-low frequency range is presented.