Granted Patent
Utility
US 6,556,687 · App. 09/253,729
Super-directional loudspeaker using ultrasonic wave
Inventor:
Koji Manabe
Patented Case
View Patent ↗
Granted: Apr 29, 2003
Filed: Feb 22, 1999
Inventor
Koji Manabe
Assignee (at issue)
NEC CORPORATION
This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.