Experimental analysis of multimicrophone probes for measurement of rocket noise.

Abstract

Although the use of multimicrophone acoustic probes can be useful in characterizing rocket noise source regions, one challenge is that both high-bandwidth pressure and intensity data are desirable. The high-frequency bandwidth limitations arise from the microphone size, type, orientation, spacing, and the design of preamplifier holders. To explore their broadband responses, various tetrahedral four-microphone probes were placed in the far field of a loudspeaker and rotated in an anechoic chamber to determine their pressure magnitude and intensity magnitude/angle errors as a function of orientation and frequency. Results are presented comparing the advantages and limitations of each design, particularly as they apply to obtaining rocket noise data. One probe design considered consists of microphones flush-mounted on a hard sphere. Other designs consist of sets of microphones arranged in tetrahedral configurations with their preamplifiers set at different angles.