A new laser vibrometry-based 2D selective intensity method for source identification in reverberant fields: part I. Development of the technique and preliminary validation

Abstract The selective intensity technique is a powerful tool for the localization of acoustic sources and for the identification of the structural contribution to the acoustic emission. In practise, the selective intensity method is based on simultaneous measurements of acoustic intensity, by means of a couple of matched microphones, and structural vibration of the emitting object. In this paper high spatial-density multi-point vibration data, acquired by using a Scanning Laser Doppler Vibrometer, have been used for the first time. Therefore, by applying the selective intensity algorithm, the contribution of a large number of structural sources to the acoustic field radiated by the vibrating object can be estimated. The selective intensity represents the distribution of the acoustic monopole sources on the emitting surface, like if each monopole would act separately from the others. This innovative selective intensity approach can be very helpful when the measurement is performed on large panels in highly reverberating environments, like aircraft cabins. In this case the separation of the direct acoustic field (radiated by the vibrating panels of the fuselage) and the reverberant one is difficult by traditional techniques. The first aim of this work is to develop and validate the technique in reverberating environments where the location and the quantification of each source are difficult by traditional techniques. The reverberant field is clearly challenging also for the proposed technique, affecting the achievable accuracy, mainly due to the fact that coherence between radiated and reverberated fields is often unknown and may be relevant. Secondly the applicability of the method to real cases is demonstrated. A laboratory test case has been developed using a large wooden panel. The measurement is performed both in anechoic environment and in simulated reverberating conditions, , for testing the ability of the selective intensity method to remove the reverberation.