X0202 3 2006-08-07 0 0000924383 AMERICAN TECHNOLOGY CORP /DE/ ATCO 0001044321 MARXE AUSTIN W & GREENHOUSE DAVID M C/O SPECIAL SITUATIONS FUNDS 527 MADISON AVENUE, SUITE 2600 NEW YORK NY 10022 0 0 1 0 Common Stock 3449081 I By Limited Partnerships Warrants A 2.67 2006-08-07 2010-04-07 Common Stock 788090 I By Limited Partnerships Warrants B 6.36 2005-07-19 2009-07-19 Common Stock 344155 I By Limited Partnerships This is a joint filing by Austin W. Marxe (Marxe) & David M. Greenhouse (Greenhouse). They share voting and investment control over all securities owned by Special Situations Fund III QP, L.P. (QP), Special Situations Private Equity Fund, L.P. (PE), Special Situations Technology Fund, LP (Tech) & Special Situations Technology II, Fund, L.P. (Tech II), respectively. 1,574,806 shares of CS, 372,466 Wts A & 164,853 Wts B are held by QP, 550,640 shares of CS, 102,564 Wts A & 75,307 Wts B are held by PE, 183,435 shares of CS, 43,385 Wts A & 14,344 Wts B are held by Tech & 1,140,200 shares of CS, 269,675 Wts A & 89,651 Wts B are held by Tech II. The interest of Marxe and Greenhouse in the shares of Common Stock owned by QP, PE, Tech, and Tech II is limited to the extent of his pecuniary interest. Austin W. Marxe 2006-08-17 David M. Greenhouse 2006-08-17