Acoustic wave scattering from flan,oed circular cylinders is considered with the Hankel-transform and mode-matching technique. The scattered field and the reflection coefficient are represented in rapidly-convergent, numerically efficient series. Numerical computations are performed to illustrate scattering and coupling behaviors in terms of aperture geometry. A cross-coupling level is shown to be less than 10 dB compared with a self-coupling in various Scattering geometries.