Method for acoustic transducer calibration
A method of acoustic transducer calibration ( 200, 400 ) using a band limited pseudo random noise source with an internal digital signal processor ( 209, 403 ) to tailor audio characteristics of an internal microphone 103 and internal speaker ( 301 ) within a communications device ( 101 ) to insure consistent amplitude and frequency characteristics of these microphone and speaker transducer devices. The method offers and advantage such that tuning of the amplitude and frequency response consistently converges to the desired filter response with a filter type offering operational stability.
1. A method for acoustic transducer calibration in a portable communications device comprising the steps of:
providing a source of pseudo random acoustical noise to a characterized external speaker source separate from the portable communications device;
directing the pseudo random acoustical noise to an input of an internal microphone used with the portable communications device;
adjusting first coefficients in at least one digital signal processor connected to the internal microphone for a desired microphone frequency response based upon the input of pseudo random acoustical noise;
discontinuing the source of pseudo random acoustical noise from the external speaker source;
applying the source of pseudo random acoustical noise to an internal speaker source in the portable communications device;
increasing the amplitude of the pseudo random acoustic noise such that it can be detected by the internal microphone;
adjusting second coefficients in the at least one digital signal processor for a desired internal speaker frequency response based upon the input of the pseudo random acoustical noise;
returning the portable communications device to an operational mode; and
utilizing a filter between the source of pseudo random acoustical noise and the external speaker to compensate for irregularities in the frequency response of the external speaker.
2. A method of acoustic transducer calibration as in claim 1 further including the step of:
comparing the output of the at least one digital signal processor with an optimal acoustic signal from the output of the pseudo random acoustic noise to provide an error signal for adjusting the coefficients of the at least one digital signal processor.
3. A method of acoustic transducer calibration as in claim 1 wherein the source of pseudo random noise is from the at least one digital signal processor.