Sound pressure measurement utilizing Light Refractive Tomography

We propose an optical measurement technique, which reconstructs the sound pressure from interferometric measurements using computed tomography. One can measure inside of liquid and solid media, as long as they are transparent to laser light. In accordance with the term Light Diffraction Tomography, we want to call the method Light Refractive Tomography, because it is based on the sound pressure-induced refractive index change along the laser beam.We utilize three tomographic reconstruction algorithms applicable to axis-symmetric beam profiles, namely, the filtered back-projection, the Hankel-Fourier method, and the onion peeling method, the latter based on Nestor and Olsens algorithm. With the help of sound field simulation we are able to generate virtual measurement data. From the quality of the reconstruction of those data, the performance of the tomographic algorithms in respect to Light Refractive Tomography can be evaluated. In addition, we determine the spatial sampling, necessary to reconstruct all details of the sound field.