Modeling the effects of modulated radiation pressure using a new acoustic lens

Abstract

Modulated radiation pressure (MRP) is a method of utilizing the acoustic radiation force by using a double-sided suppressed carrier modulated (DSB-SCM) signal. This produces a modulated signal that oscillates at twice the modulation frequency. This process facilitates target detection and classification by using a high-carrier frequency to probe the target and shake it with the low-modulation frequency, which can be designed to be commensurate with the vibrational modes of the target. A frequency sweep can estimate the target resonant frequencies, while a physical scan along its length can estimate its mode shapes. Recently, a series of experiments were conducted at Washington State University with a newly designed and fabricated acoustic lens with a one-meter focal length. These experiments demonstrated that the first few bending modes of scaled targets like a solid aluminum cylinder and an open-ended aluminum cylindrical shell could be excited by MRP at a standoff distance of one meter and target mode shapes were measured using a physical scan. In this presentation, we show modeling results that confirm experimental findings: (1) estimation of target resonant frequencies using a frequency sweep and (2) estimation of target mode shapes using a physical scan.