Automatic microphone calibration for video teleconferencing

A method of automatically calibrating an audio input device, the audio input device having a gain affecting operation of the audio input device, the method comprising the steps of:

• (a) receiving an input signal generated by the audio input device in response to an audio input;
• (b) sampling the input signal to produce a plurality of samples;
• (c) detecting a plurality of instances of voice energy in the samples;
• (d) creating a power density function (PDF) from the plurality of instances of voice energy, the PDF including a signal level that is defined with respect to said PDF, the signal level differing from a voice reference level by an offset amount;
• (e) upon detecting a predetermined number of consecutive instances of voice energy in the samples, adjusting the gain according to the offset amount;
• (f) repeating steps (a) through (d), such that a plurality of PDFs are generated, the plurality of PDFs including a plurality of extreme data values;
• (g) discarding the extreme data values to generate a revised signal level from at least one of the PDFs, the revised signal level differing from the voice reference level by a revised offset amount;
• and
• (h) adjusting the gain according to the revised offset amount.

An apparatus for controlling an operating parameter of an audio input device, the audio input device generating an input signal in response to an input, the apparatus comprising:

• a voice activity detector detecting voice occurrences in the input signal and determining a noise floor based on the input signal,
• a function generator receiving the voice occurrences and generating a voice power density function (VPDF) from the voice occurrences, the VPDF defined along a range of signal levels, the range of signal levels including a voice reference level, the voice reference level having a position along the range of signal levels relative to the VPDF;
• an adjuster changing the value of the operating parameter according to the position of the voice reference level along the range of signal levels relative to the VPDF;
• and
• a gain limiter, the gain limiter limiting the adjuster so that the noise floor does not exceed a noise reference level when the operating parameter is adjusted.

An apparatus for automatically calibrating an audio input device having an operating parameter, the apparatus comprising:

• means for receiving an input signal generated by the audio input device in response to an audio input;
• means for determining a noise floor based on the input signal;
• and
• means for adjusting the operating parameter based on the input signal, including means for limiting said adjusting so that the noise floor does not exceed a noise reference level when the operating parameter is adjusted.

A system capable of duplex audio communication with a remote site, the system comprising:

• processor means for controlling the system;
• input means for inputting audio information to be transmitted to the remote site, the input means having an operating parameter affecting operation of the input means;
• output means for outputting audio information received from the remote sight;
• and
• voice detection means for detecting voice in an audio signal received by the system or to be transmitted by the system, the voice detection means determining a noise floor based on the audio signal;
• calibration means for calibrating the input device, the calibration means including:
• means for adjusting the operating parameter based on the audio signal, including means for limiting said adjusting so that the noise floor does not exceed a noise reference level when the operating parameter is adjusted.

A communication system comprising:

• a processor controlling operation of the system;
• an audio input device coupled to the processor and coupled to input audio information to be transmitted to the remote site, the audio input device having an operating parameter;
• an audio output device coupled to the processor and coupled to output audio information received from the remote sight;
• and
• a voice detector coupled to detect voice in an audio signal received by the system or to be transmitted by the system, the voice detector generating a noise floor;
• and
• a calibrator including
• an adjuster changing the value of the operating parameter by an adjustment amount;
• and
• a gain limiter limiting the adjustment amount so that the noise floor does not exceed a noise reference level when the operating parameter is adjusted.