Abstract
Near-field acoustic holography (NAH) has been shown to be a powerful tool for the study of sound radiation from vibrating structures. It provides the reconstruction of the normal surface velocity from pressure measurements made using a microphone array near the vibrating structure.
However, the prediction of the vibration properties may sometimes be a difficult task, due, for example, to the presence of several uncorrelated sources.
In order to validate the reliability of NAH results in terms of surface velocity, measurements taken by a laser Doppler vibrometer were used for comparison in this work.
Initially, the acoustic radiation of a muffler for automotive application, excited by a shaker, was measured in a semi-anechoic room by NAH, at different frequencies.
The distribution of the vibration velocities in correspondence of the plane tangent to the curved surface of the muffler obtained using NAH was compared to the vibration map measured by the laser instrument. Comparisons allowed the determination of the degree of accuracy in the
NAH measurements and calculations.
This study was conducted within the European Growth Project ACES (Optimal Acoustic Equivalent Source Descriptors for Automotive Noise Problems) GRD1-1999-11202.