Abstract:

Broadband signals are commonly used in ultrasonic spectroscopy to measure the frequency-dependent attenuation characteristics of lossy solid media. As compared with narrow-band signals, broadband signals are preferred since they do not require tedious frequency scanning and extensive data reduction efforts. By using spread spectrum techniques to design signals with given bandwidth and temporal characteristics, the overall accuracy and resolution of ultrasonic spectroscopy can be improved. An expression for ultrasonic attenuation is developed and compared with the traditional analysis approach to illustrate the improved accuracy of the new technique. Experimental results obtained using a direct sequence modulation system will also be presented for the attenuation spectra of various lossy solids.