Study of the strategies of tuning a spinning sound mode generator

The following strategies for tuning a spinning sound mode generator are considered: 1) maximizing the dynamic range between the target mode and the other modes in the duct; 2) minimizing the discrepancy between the calculated and experimental distribution of acoustic pressure at the microphones in the duct; 3) minimizing the discrepancy between the calculated and experimental distribution of acoustic pressure at the far-field microphones. A generator of 8 acoustic drivers with a circular cross-section duct with a diameter of 0.23 m was used. Measurements were carried out with both microphones installed flush into the duct wall (a circular array of 20 microphones, an axial array of 11 microphones and 8 additional microphones) and far-field microphones (10 microphones were installed on an arc with a radius of 2 m from the axis of the generator duct section center in the range of the polar angle varying from 0 to 90 degrees in equal increments). The experiments were conducted in an acoustic anechoic chamber at PNRPU. It was established that all the proposed strategies for tuning the spinning sound mode generator are feasible, because in all cases, when tuning the generator, it was possible to improve the considered characteristics of the sound field (increase the dynamic range of the target mode or obtain the distribution of sound pressure over the microphones closer to the calculated one) relative to the initial state.