Optimal and wavelet-based shock wave detection and estimation
Brian M. Sadler, Tien Pham, Laurel C. Sadler · The Journal of the Acoustical Society of America · 1998
Detection and estimation of aeroacoustic shock waves generated by supersonic projectiles are considered. The shock wave is an N-shaped acoustic wave emanating in the form of an acoustic cone trailing the projectile. An optimal detection/estimation scheme is considered based on a parametric signal plus white Gaussian noise model. To gain robustness and reduce complexity, we then focus on gradient estimators for shock wave edge detection, exploiting the very fast shock rise and fall times. The approach is cast in terms of a wavelet transform where the level of smoothing corresponds to scale. A multiscale analysis is described, consisting of multiscale products, to enhance edge detection and estimation. This method is effective and robust with respect to unknown environmental interference that will generally not exhibit singularities as sharp as the N-wave edges. Experimental results are presented for discriminating N waves in the presence of vehicle noise. Results are also shown, as a function of miss distance, for gradient-based detection of simulated small projectile shocks inserted into recorded tank noise.