Higher-order Modes Decomposition and Measurement in Ducts Using Single Microphone

Abstract:

A new method for decomposing and measuring higher-order mode waves in ducts using single microphone is proposed in this paper. The method is based on a repeatable inspiriting sound source associated with a slowly moving microphone along central axis of the duct. Compared with previous research, some problems such as microphone matching can be avoided, and much more modes can be obtained. At first the basic principle of modes decomposition, as well as single-microphone measurement system is described. Then the effectiveness of this method is verified by comparing the test results with those of the standard measurement in standing wave tube. Finally some experimental studies in a 600mm square waveguide are discussed.