Abstract: An adaptive sound masking and/or scrambling system and method portions undesired sound into time-blocks and estimates frequency spectrum and power level, and continuously generates white noise with a matching spectrum and power level to mask the undesired sound.

Abstract: An adaptive sound masking system and method portions undesired sound into time-blocks and estimates frequency spectrum and power level, and continuously generates white noise with a matching spectrum and power level to mask the undesired sound.

Abstract: The invisible acoustic screen for reducing sound leakage from handsfree telephones, loudspeaking computer terminals, and the like in a workspace includes a sound reducing apparatus comprising: a sound producing loudspeaker; a cancelling loudspeaker; a sensing microphone having an output; a delay circuit; and, an adaptive filter circuit having a value determined by a transfer function between the sound producing loudspeaker and the sensing microphone and by a transfer function between the cancelling loudspeaker and the sensing microphone; and the output of the sensing microphone being fed back to the adaptive filter circuit; and the received signal coupled through a delay circuit to the sound producing loudspeaker.

Abstract: A microphone unit particularly suitable for conference applications is provided, wherein an acousto-electric transducer is disposed between two dish-like back-to-back sound collectors, each having a central aperture exposing one side of the transducer, which preferably has a single planar diaphragm.

Abstract: A telephone group listening system is one in which one member of an assembled group has a telephone for communication with a remote party while the other members may only listen to the communication through the agency of a loudspeaker. The system is subject to the Larsen effect on call answering or clear down if the telephone handset is normally sited close to the loudspeaker. This effect is overcome by including a proximity switch in the loudspeaker circuit, the switch being triggered by a change in the level of coupling of a capacitively or inductively coupled circuit, the coupling being dependent on the closeness of the speaker's body to the switch or on the separation of the handset and the loudspeaker.

Abstract: A telephone apparatus for use in a conference room has a housing, with a vertical central axis, with a loudspeaker at the upper end, coaxial with the vertical axis, and a microphone at the lower end. The loudspeaker faces upward with an unrestricted outlet and is omnidirectional in output. The microphone faces downward and is coaxial with the vertical axis, being sensitive only to airborne vibration only. The microphone is surrounded by an inclined surface extending outwardly and upwardly at an angle of about 30.degree., and has an omnidirectional sensitivity. The housing is supported with the microphone inlet about 1/2 inch above a surface, which can be the surface of a base member attached to the housing. The minimal peripheral distance from the center line of the speaker to the center line of the microphone, around the housing, is about 15 inches, for good acoustic separation. A resonator can be attached to the microphone inlet.