Abstract
Data regarding the Johns Manville hemi-anechoic chamber qualification according to ISO 3745 Annex A and ANSI S12.35 Part 9 were presented at ASA/NoiseCon in December 2000. In addition to techniques based on these standard test methods, an alternate qualification technique was devised using a pressure–pressure intensity probe. The basis of the technique stems from the fact that the sound pressure and intensity should be nearly equal in a free-field environment. The difference between the sound pressure and sound intensity at a point is known as the pressure-intensity index (p-i index), a common ISO measure of source strength. P-i index measurements were made along several measurement paths and at discrete points at the predicted boundaries of the room. Results of this nonstandard test were compared to those of traditional qualification techniques. Although the method uses a possibly uncommon instrument, the results suggest a greater tolerance for various sound sources and allow for quick computation of chamber qualification.
Published Version
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