In this paper, the effect of transducer focusing on the integrity of ultrasonic backscattering measurements is examined. The rationale for this study stems from our observation that the calculated values of backscattering coefficients from data obtained with nonfocused transducers are always substantially lower than those obtained with focused transducers when the standard substitution method is used for backscattering measurements. It is postulated that this discrepancy is caused by the extremely complicated beam behavior of a focused transducer. This hypothesis is verified experimentally. It is therefore concluded that focused transducer could yield misleading results when a standard substitution method is used for absolute backscattering measurements.
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