An electro-acoustic terminal unit for use in an audio teleconferencing system comprises a loudspeaker and one or more microphones each having a sensitivity which is directionally dependent and exhibits at least one null or substantially null position. The loudspeaker and microphones are rigidly mounted on a boom and the microphones are so located and orientated relative to the loudspeaker that the null position is directed towards the loudspeaker.
An electroacoustic transducer apparatus which prevents oscillations as a result of acoustic coupling between an acoustic-wave transmitter and a receiver. The transmitter and receiver each comprise an electro-acoustic transducer network. The transducers in each network are arranged so that the phase and amplitude of the signals applied to the transmitter transducers and the signals supplied to an adder circuit by the receiver network transducers (25) to (30) of the receiver network are such that in the oscillation frequency band the radiation pattern of the transmitter network and the directivity pattern of the receiver network are zero in at least one direction. The two networks are arranged relative to each other so that the directions of minimum radiation and directivity correspond to the directions of maximum coupling between the transducers of the two networks.
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.
A method and apparatus for alleviating sound-coupled feedback in a conference room having a conference table for the seating of human participants, the room sound system including one or more loudspeakers for outputting amplified sound from a given source in sufficient volume for all to hear plus one or more microphones for picking up the voice of any given participant. By locating the loudspeaker(s) below the board-like table top, preferably at floor level attached to the table foot structure, and by locating the microphone(s) above the table top, preferably in the central region, sound waves from the loudspeaker(s) are directed with high efficiency coupling to the participants' ears, but are constrained by the table top to "feedback" to the microphone(s) only with low efficiency coupling. "Rain barrel" effects are reduced. The invention finds advantageous use in purely local conference room sound amplification systems and in teleconferencing systems.
A microphone and loudspeaker arrangement for use in a teleconference system, wherein a plurality of microphones are held in a fixed relationship to a loudspeaker. The microphones are independently gated ON in response to (1) speech picked up by the microphone, (2) a loudspeaker signal driving the loudspeaker and (3) an electrical signal related to the microphone signals of the other associated microphones. A noise adapting threshold circuit generates a voltage level representative of background noise which is compared with the microphone signal of a respective microphone for determining whether the microphone is receiving speech. A decisional circuitry monitors the microphone signal of the associated microphone with respect to a MAX bus which carries microphone signals representative of the level of microphone signals at the other microphones. The decisional circuitry generates a signal indicating that the associated microphone is the first loudest microphone signal.
A compact personnel monitor speaker system for live music sound reinforcement monitoring introduces insignificant electrical loading and reliably connects directly to high power audio amplifiers. The monitor speaker includes a device for mounting onto a microphone stand, music stand or other stand in close proximity to the user.
