| Popis: |
The Kirchhoff approximation has been used in deriving the reverberant tail ps, which results when a short spherical pulse of strength F(t) backscatters from a rough pressure‐release surface. The amplitudes of the differential scattered pulselets producing ps depend on the displacement and slope of the surface elements at which they originate, the functional form of both F and F′, and also certain geometric weighting factors determined by the location of the elements. More‐specific insight is obtained from hs, the component due to scattering in the impulse response h = h0 + hs, of the “ocean‐surface filter.” The tail portion of hs may be expressed as a “ring average” of two terms, one of which involves the slope, the other the curvature of the surface. Near the specular region, the term involving slopes is dominant generally; later, the curvature term gains the upper hand. Specific calculations of 〈ps2〉uv for incident sine‐wave pings and explosive pulses reflecting from randomly rough surfaces are compared... |
