The reciprocal technique was used to evaluate the noise transmission characteristics of an aircraft fuselage, which can be used for validating computer models, or for evaluating noise reduction methods. The aircraft fuselage was divided into a number of scan elements, and the transfer function between interior noise and the response on each element was combined with a specified computed external propeller sound pressure field to predict the interior noise at specified locations. The reciprocal approach uses a nonopole noise source inside the aircraft, and a capacitance probe to measure the fuselage surface response. The approach was validated by comparing the direct transfer function for one element with the reciprocal measurement. The total time needed to perform the scan could be reduced by reducing the number of fuselage elements scanned. Analysis of the data indicated that a reasonable prediction of internal noise is obtained if only those external elements on which the propeller sound pressure field is within 10 dB of the peak are measured. Further improvements could be made with a lighter scanner to reduce operator strain, or an automated system for moving the scaner. The probe offset distance could also be automatically measured, and actively controlled by some displacement actuators within the scanner. This would reduce the requirements on the operator, and improve accuracy. Only two internal noise source locatios were used to predict the noise due to the propeller at two interior locations. Additional noise sources, or an automated approach to moving those used, would be useful in obtaining noise predictions throughout the cabin. The key advantage of the reciprocal approach is that once the transmission information is obtained for a given internal location, the noise at this location can be predicted for any external sound pressure distribution.


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    Title :

    Aircraft fuselage noise transmission measurements using a reciprocity technique


    Additional title:

    Schallübertragungsmessungen am Flugzeugrumpf mittels einer Reziprozitätstechnik


    Contributors:

    Published in:

    Publication date :

    1995


    Size :

    17 Seiten, 15 Bilder, 2 Tabellen, 15 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English






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