Yoko Yamakata Michiaki Katsumoto Toshiyuki Kimura Directional Sound Radiation System Using a Large Planar Diaphragm Incorporating Multiple Vibrators. 1399-1407 2009 92-A IEICE Transactions 6 http://search.ieice.org/bin/summary.php?id=e92-a_6_1399&category=A&year=2009&lang=E&abst= db/journals/ieicet/ieicet92a.html#YamakataKK09