Computer controlled adaptive speakerphone

Abstract

An improved switched-loss, adaptive speakerphone dynamically adjusts its switching thresholds and other performance parameters based on an analysis of acoustic environment and telephone line conditions. To access these conditions, the speakerphone utilizes a computer with associated firmware. As part of a calibration process, the speakerphone computes its thresholds before each use to compensate for possible variations in hardware circuitry therein. This is achieved by passing a first and then a second level of a test tone signal through the hardware circuitry and measuring the resulting response. The speakerphone also measures the acoustics of the room in which it operates as part of the calibration process. For this measurement, a tone burst signal is generated through a loudspeaker in the speakerphone and measured by a microphone also in the speakerphone. A time-domain acoustic response of the room is obtained which provides to the computer the amplitude of the return signal and the duration of its echo. The calibration process is also applied to the speakerphone's interface to the telephone line through a hybrid. While in use, the degree of hybrid reflection is measured and the result provided to the computer. With the information on both the acoustic environment and the hybrid, the adaptive speakerphone is able to adjust on a real time basis the amount of switched loss and threshold switching levels between operating states to suit existing conditions. If, for example, the speakerphone is attached to a good telephone line and is in a good acoustic environment, it will provide the user with near full to full duplex performance.