by using a single aperture of dimensions not greater than the shortest operating wavelength

Full Title

Details of transducers > Arrangements for obtaining desired frequency or directional characteristics > for obtaining desired directional characteristic only > by using a single transducer with sound reflecting, diffracting, directing or guiding means > by using a single aperture of dimensions not greater than the shortest operating wavelength

Classification Context

Section:

ELECTRICITY

Class:

ELECTRIC COMMUNICATION TECHNIQUE

Subclass:

LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS