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  System and method for microphone gain adjust based on speaker orientationUSPTO Application #: 20060133623Title: System and method for microphone gain adjust based on speaker orientation Abstract: A system and method for automatically adjusting the gain of an audio system as a speaker's head moves relative to a microphone includes using a video of the speaker to determine an orientation of the speaker's head relative to the microphone and, hence, a gain adjust signal. The gain adjust signal is then applied to the audio system that is associated with the microphone to dynamically and continuously adjust the gain the audio system. (end of abstract)
Agent: Rogitz & Associates - San Diego, CA, US Inventors: Arnon Amir, Gal Ashour USPTO Applicaton #: 20060133623 - Class: 381092000 (USPTO) Related Patent Categories: Electrical Audio Signal Processing Systems And Devices, Directive Circuits For Microphones The Patent Description & Claims data below is from USPTO Patent Application 20060133623. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates generally to adjusting the gain of one or more microphones based on the position and/or orientation of a speaker relative to the microphones. [0003] 2. Description of the Related Art [0004] Audio systems, including stage systems, teleconferencing and video conferencing systems, lecture videotaping and distance learning systems, mobile telephones, and other media typically include one or more microphones for receiving a person's voice, an amplifier that amplifies the output of the microphone, and an audio speakers that plays the amplified sound. Ordinarily, when an audio system is calibrated, the volume output by the audio speaker is adjusted (by, e.g., adjusting the amplifier gain) to a desired volume for the case where a person speaks directly into the microphone. This can be thought of as calibrating the system for a 0.degree. orientation of the person's head relative to the microphone, at a nominal mouth-to-microphone distance. [0005] Should the speaker move away from the microphone or turn her head away from the 0.degree. orientation, however, the sound level at the microphone is less than what the system was calibrated for. The audio speaker volume accordingly decreases, which can be annoying and distracting. On the other hand, if the system is calibrated for a head orientation of other than 0.degree., when the person subsequently speaks directly into the microphone the audio speaker volume increases, again potentially distracting the intended recipient or recipients from what the person is saying. [0006] The common approach to resolving the above-noted problem is to physically hold the microphone in a single location in front of the person's mouth, either by clipping the microphone to the person's clothes, by suspending the microphone from a head-worn harness in front of the person's mouth, or by training the person to steadily hold the microphone in front of her mouth. All of these approaches suffer drawbacks. Even when a microphone is clipped to clothing, the person can turn her head away from the microphone to an orientation other than that for which the system was calibrated. Many people do not like to wear harnesses on their heads, and even experienced stage performers can temporarily wave a hand held microphone away from their mouths without intending to. [0007] Accordingly, the present invention recognizes that it would be desirable to automatically adjust the gain of an audio system in synchronization with the head movements of a speaking person relative to a microphone. Past attempts at automatic gain adjust do not use actual speaker motion to adjust gain, but instead are based on attempting to vary gain to establish a baseline audio output in response to varying received audible levels, which at best are indirectly related to speaker motion. Representative of such systems are those disclosed in U.S. Pat. Nos. 5,640,490, 5,896,450, and 4,499,578. Unfortunately, a speaker might deliberately vary her voice volume, a speaking technique that is frustrated by systems that establish amplifier gain based only on received audio signals. The present invention understands that it would be desirable to more precisely adjust audio system gain based on actual speaker movement relative to a microphone or microphones. The present invention also recognizes that conventional AGC may amplify background noise when the speaker is silent. SUMMARY OF THE INVENTION [0008] The invention is a general purpose computer programmed according to the inventive steps herein. The invention can also be embodied as an article of manufacture--a machine component--that is used by a digital processing apparatus and which tangibly embodies a program of instructions that are executable by the digital processing apparatus to undertake the logic disclosed herein. This invention is realized in a critical machine component that causes a digital processing apparatus to undertake the inventive logic herein. [0009] In one aspect, a computer-implemented method is disclosed for generating a speaker gain adjust signal to establish an audio output level. The method includes receiving a person-microphone position signal representative of a position of a person relative to a microphone, and determining a gain adjust signal based on the person-microphone position signal. The method further includes using the gain adjust signal to establish the audio output level. [0010] In a preferred embodiment, the person-microphone position signal is derived from a video system, but it could also be derived from a motion or position or orientation or distance sensing system, a laser system, a global positioning system, or other light receiving system. The gain adjust signal can be determined based on the distance from a person's mouth to a microphone, or an orientation of a person's head relative to the microphone, or both. Alternatively, the gain adjust signals can be determined from a mapping of calibration person-microphone position signals to calibration audio levels. In any case, the gain adjust signals can be determined contemporaneously with the recording of the person, or determined after the recording of the person. A slow response gain adjuster such as a Kalman filter can also be used to stabilize variations in audio levels caused by rapid movement of the person. [0011] In another aspect, a computer is programmed to undertake logic for dynamically establishing a gain of an audio system. The logic includes receiving a video stream representative of a person and a microphone, and deriving person-microphone position signals using the video stream. The logic also includes using the person-microphone position signals to generate audio gain adjust signals for input thereof to the audio system. [0012] In still another aspect, a computer program product includes computer readable code means for receiving light reflection signals representative of light reflected from a person and light reflected from a microphone. Computer readable code means, based on the light reflection signals, determine an orientation signal. Also, computer readable code means generate an audio gain adjust signal based on the orientation signal. [0013] In another aspect, an audio system includes a microphone electrically connected to an audio amplifier having an audio gain. The system also includes a video camera and a processor receiving signals from the video camera and establishing the audio gain in response thereto. [0014] In yet another aspect, an audio system includes a microphone electrically connected to an audio amplifier having an audio gain. The system also includes a source of person-microphone position signals and a processor receiving signals from the video camera and establishing the audio gain in response thereto. [0015] The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which: BRIEF DESCRIPTION OF THE DRAWINGS [0016] FIG. 1 is a schematic diagram of the present system; [0017] FIG. 2 is a flow chart showing the overall logic of the present invention; [0018] FIG. 3 is a flow chart showing the logic for automatically determining a speaker-to-microphone gain mapping; and [0019] FIG. 4 is a block diagram of a system that generates a fast gain adjust signal based on head orientation and a slow gain signal based on the audio stream. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0020] Referring initially to FIG. 1, a system is shown, generally designated 10, which includes a digital processing apparatus, such as a computer or processor 12, which has a local or remote gain adjust module 14 that embodies the logic disclosed herein. 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