RESUMEN
This study deals with the reconstruction, from ultrasonic measured data, of the sound speed profile of a penetrable two-dimensional target of arbitrary cross-section embedded in an infinite medium. Green's theorem is used to obtain a domain integral representation of the acoustical scattered field, and a discrete formulation of the inverse problem is obtained using a moment method. An iterative non-linear algorithm minimizing the discrepancy between the measured and computed scattered fields is used to reconstruct the sound speed profile in the region of interest. The minimization process is performed using a conjugated-gradient method. An experimental study with significant acoustical impedance contrast targets immersed in water was performed. Images of the sound speed profile obtained by inversion of experimental data are presented.
Asunto(s)
Interpretación de Imagen Asistida por Computador/métodos , Dinámicas no Lineales , Sonido , Ultrasonido/métodos , Ultrasonografía/métodos , Algoritmos , Simulación por Computador , Movimiento (Física) , Análisis Numérico Asistido por Computador , Fantasmas de Imagen , Dispersión de Radiación , Factores de Tiempo , Transductores , Ultrasonido/instrumentación , Ultrasonografía/instrumentaciónRESUMEN
The detection of multicomponent signals for which the components are not equidetectable is precisely investigated as a function of the level difference ΔL(i∕j) between components. The detection thresholds are determined for a seven-tone complex signal with random starting phases masked by white noise. Level differences between the components are examined. A model for non-equidetectable conditions based on the statistical summation model is described. The improvement in detection is calculated from the level difference between components that is related to the thresholds for single components. The model predictions are in accordance with the experimental results.