Visualization of acoustic intensity vector fields using scanning measurement techniques

Abstract

Sound propagation paths are not always well understood mainly because of the complex nature of the source or the environment. A direct method to capture the sound energy flow throughout a room is to measure the three-dimensional sound intensity distribution across space. In the past years, several studies have been carried out using step by step measurements with a three-dimensional intensity probe consisting of a sound pressure transducer and three orthogonal particle velocity sensors. The probe’s ability to measure even in highly reverberant environments and its small size are key features required for numerous applications. However, punctual measurements are time-consuming, especially when a large number of measurement positions are evaluated. The use of advanced scanning measurement techniques, such Scan & Paint, allows for the gathering of data across a time stationary sound field in a fast and efficient way, using a single sensor and webcam only. The acoustic signals are acquired manually by moving a probe across a measurement plane whilst filming the event with a camera. In the post-processing stage, the sensor position is extracted and then used for linking a segment of the signal acquired to a certain position of the space. In this manner, the overall measurement time is reduced from hours to minutes. In this paper, the acoustic intensity vector fields of several complex examples are investigated; revealing the acoustic energy flow of several vehicles, a loudspeaker in a room, and also the interaction between an absorbing sample and a reverberant sound field.

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