Validation of the cylindrical microphone array for measuring sound power levels of noise sources

Abstract

Recent papers have (i) introduced the concept of the cylindrical microphone array for the measurement of sound power levels of noise sources as an alternative to the parallelepiped and hemispherical arrays [M. A. Nobile and J. A. Shaw, Proc. Inter-Noise 99], (ii) set forth a detailed procedure for using the cylindrical array that could readily be incorporated into international standards [Nobile et al., Proc. Noise-Con 2000], and (iii) presented the results of measurements using that procedure on a 1.75-m-high noise source using a variety of microphone positions to draw conclusions regarding the number of microphones, equal versus unequal areas, and traversing versus fixed-point implementations [Nobile et al., Proc. Inter-Noise 2002]. The cylindrical array has since been incorporated into ISO 7779 and is being proposed for inclusion in the upcoming revision of ISO 3744. In an effort to gain experience with this new array and to help validate its use, a prototype rotating cylindrical array was constructed, and measurements were taken on a variety of noise sources. The results are compared to those taken with the well-established hemispherical microphone array, using 40 coaxial circular paths.