Experimental characterization of shock formation distance in broadband noise propagation.

Abstract

Unlike initially sinusoidal waveforms, the definition of the “shock formation distance” for broadband noise is complicated by the fact that not all shocks form at the same rate. Examination of the concept of a “characteristic” shock formation distance for broadband noise raises some questions: Is there some generalization of the shock formation distance for sinusoidal signals or narrowband noise that can be applied to broadband noise? If so, is it inversely proportional to amplitude and frequency, as the pure tone and narrowband noise distances are? Possible methods to investigate these questions, such as statistical analyzes and examining spectral slopes and time waveform derivatives, are discussed. These techniques have been studied using experimental data acquired from finite-amplitude broadband noise propagation in an anechoically terminated plane-wave tube. Preliminary results from these experiments are discussed.