Removing distortions from ground sonic boom measurements for certification of over land flight

Abstract

Ground measurements of sonic booms contain distortions acquired during their propagation through the atmosphere that greatly changes their loudness. Quiet shaped boom vehicles are being proposed for acceptable over land flight. Because of distortion loudness variations, many ground measurements would be needed to develop accurate statistics of loudness. And highly turbulent atmospheres increase loudness variations and affect average loudness, so a limited range of atmospheric conditions would be required for a certification procedure of acceptable loudness. More flights and limited conditions would substantially increase vehicle certification cost. A measurement de-turbulencing technique is shown to greatly reduce atmospheric distortions. It improves loudness accuracy to (hope to quantify) from a single pass over a line of at least 25 microphones. The method combines a de-turbulencing technique developed by Plotkin, with a spatial averaging technique used in wind tunnel measurements of sonic boom, and wit...