The BBC reports Imperial College London has demonstrated how to produce an= =20 acoustic cloaking device. essentially it an array of plastic sheets with an= =20 array of strategically drilled holes. http://www.bbc.co.uk/news/science-environment-13905573 Colin -- cdb, 3/07/2009 =20 -- colin@btech-online.co.uk --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .