Assessment of directivity of real noise sources- Application to vehicles.

Abstract: The aim of this project is to evaluate a new method for noise directivity measurements; whether a room correction factor can be used to compensate for the effect of a light reverberation field. Another aim is to find if there is any suitable standard to use. No standard to use fully was found, but SS-EN ISO 3744:2010 has a method to compensate for reverberation upon which the present method is based. Measurements were performed for three objects in a semi anechoic room and two ordinary rooms. Sound pressure was measured for all multiples of 30° in the horizontal plane where the acoustic centre for each object was situated. Thereafter, the room correction factor was calculated and from that compensated values could be found. The room correction factor did not fully make the wanted difference. The results only showed subtle connections, but tendencies show that the method might be valid for 250 and 500 Hz. To get a stronger correlation, the method must be refined. The distance to the microphone is for example one factor that depends on the environment.