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This paper describes an application of active control of sound diffracted by a barrier. The basis of this application is the cancellation of the sound pressure at the diffraction edge, which behaves like a virtual source to the diffracted field. Several points on the edge were canceled simultaneously by several secondary sources to get a large attenuation over a wide area. While many factors appear to influence the effectiveness of active control, the points of cancellation on the diffraction edge and the arrangement of the secondary sources were studied. The optimum conditions for control were investigated using numerical simulation. These conditions were then confirmed experimentally using multichannel adaptive signal processing. It was found that control is stable and effective when the intervals of the points of cancellation on the edge are shorter than half of the wavelength, and that attenuation is greatest when the secondary sources are nearest the primary source.

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A tiny interstitial deletion of 7p was found in a 5-month-old boy with a craniosynostosis and many anomalies. His karyotype was 46,XY,del(7)(p15.3p21.3). Here we present not only further evidence of an association between craniosynostosis and 7p monosomy, but also deletion mapping to indicate that the critical segment for craniosynostosis lies in the mid-portion of 7p21, that is at 7p21.2 or the proximal part of 7p21.3.