An Educational Model and Toolbox for Acoustic Tomographic Imaging

Abstract

A model apparatus is presented which has been especially designed for educational purposes and experimental testing of tomographic algorithms. The system is similar to an acoustic tomographic system which has been developed to observe local differences in the sound speed in order to recalculate images of physical parameters which influence the sound speed fields under natural conditions. The system has been successfully used for investigations of atmospheric non-homogeneities (horizontal temperature and wind velocity fields, surface effects) by means of travel-time measurements of acoustical signals. This technique has been extended to a more general environment. The basis is an acoustic multi-channel spectrometer operating in the audio range. The model spectrometer completely controls the acoustical experiment (emission and reception). The modular approach is implemented over several levels including the real-time DSPsoftware, the driver for the acoustic spectrometer and the data-processing concept. The controlling software and the algorithmic part have been developed within the framework of a general toolbox concept for acoustic spectrometers. Fundamental aspects of the signal processing in the tomographic experiment form part of the educational approach. For instance, the influences of various acoustic signatures such as MLS (maximum length sequences) can be demonstrated. The extension of the transportable model enables frequency- and travel-time scaled experiments within the audio and nearultrasonic range.