Analysis of scattered sound from underwater hollow cylinders using the Wigner distribution function

The scattered sound from an aluminum hollow cylinder in water is analyzed u sing the Wigner distribution function. When sound is scattered by a thick-s helled cylinder, the creeping wave appears after the specular-reflected wav e. As the thickness of the cylinder shell decreases, however, the creeping wave tends to disappear and ridges parallel to the time axis come into the time-frequency plane because of the resonance in the cylinder. While the ba ckscattered wave exhibits a complicated distribution pattern, the wave scat tered at 90 degrees is relatively monotonic. From the computer simulation t hat the removal of the transverse wave propagating in the cylinder results in the emphasis of the specular reflection and the pattern becomes monotoni c in the time-frequency plane, the presence of the transverse wave influenc es strongly the characteristics of the scattered sound from an elastic obje ct. Since the distribution in the plane exhibits a characteristic pattern i n every case, the Wigner distribution function offers an effective means to analyze the scattered sound from an object in water.