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Acoustical imaging techniques are providing today new powerful ways to investigate in detail relatively complex fields.HETRAVIB R.D.S. has acquired a broad theoretical and practical experience of.The main application of these techniques is to classify major noise sources in order to applysignificant and efficient noise reducing techniques.In this paper a systematic procedure of analysis and field description is presented ; this method allows quick and accurate evaluation of the efficiency of various modifications ins helicopter (acoustic and damping materials).This procedure relies on the use of energetic and spatial criteria to analyse acoustic fields by means of nearfield multi sensor acoustic arrays. -PROBLZH DESCRIPTIONHelicopters structures and cockpitare submitted to very high vibration levels, typically 2 to 3 times higher than in a conventionnal aircraft.This situation leads to high noise levels in a very broad frequency range.Excitation sources are numerous r main and rear rotors, engines, gearbox and other prime movers.
Berhault et al. (Wed,) studied this question.