Jet noise source location by acoustic beamforming and nearfield sound contours - A comparison

Abstract

The knowledge of the distribution of sources of noise for various frequencies in a jet are often needed to understand the jet noise mechanisms and to predict and control jet noise. This knowledge can also be very helpful for extrapolating nearfield noise to the farfield and vice versa. Many techniques have been developed over the years to measure jet noise source locations; however, most of them are extremely time consuming and rather cumbersome. The more recently developed acoustic beamforming technique is quite rapid, but its performance against older techniques has never been examined. This study attempts to do precisely that by acquiring source location data for the same jet, first by the beamforming methodology and then via the well-established nearfield contour method. Both methods are employed to obtain source locations of a small one-inch exit diameter conical jet for subsonic conditions, and it is shown that both methods provide similar results. Additional confirmation is obtained on jets with unmodified and tabbed exit conditions.