Precision grade sound power measurement using the sound intensity scanning technique: Comparison of methods for accuracy estimation

Abstract

To assist the development of a precision scanning intensity standard for sound power determinations, this study investigated two accuracy estimation methods proposed by ISO Working Group 25. One method used the F4 sampling criterion from the precision grade discrete point intensity standard [ISO 9614-1:1993], adapted for the scanning intensity technique. The other method assumed that measurement accuracy was related to the difference between measurements using two different scanning paths. This method was a variation of the repeatability test from the engineering grade scanning intensity standard [ISO 9614-2:1996]. The study compared the estimated accuracy from each of the two methods to a third accuracy estimate, the difference between a sound power determination using the scanning intensity technique and a precision grade measurement using sound pressure [ISO 3745:1977]. All measurements were made under hemi-anechoic conditions and all intensity scannning was done manually. Results were obtained for the following three sound sources: a Bruel & Kjaer reference source, a vacuum cleaner, and a loudspeaker. The results suggested that both of the proposed methods can be of use in achieving precision grade accuracy.