An acoustic device is provided with first and second one or more acoustic elements to generate a first signal that includes mostly undesired audio and substantially void of desired audio, and a second signal that includes desired as well undesired audio respectively. The first one or more acoustic elements...http://www.google.de/patents/US7386135?utm_source=gb-gplus-sharePatent US7386135 - Cardioid beam with a desired null based acoustic devices, systems and methods
