A new laser vibrometry-based 2D selective intensity method for source identification in reverberant fields: part II. Application to an aircraft cabin

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 practice, 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, as if each monopole
acted 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, such as 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 work shown in this paper is the application of part of the results of
the European project CREDO (Cabin Noise Reduction by Experimental and Numerical
Design Optimization) carried out within the framework of the EU. Therefore the aim of this
paper is to illustrate a real application of the method to the interior acoustic characterization of
an Alenia Aeronautica ATR42 ground test facility, Alenia Aeronautica being a partner of the
CREDO project.