Built-in microphone device

A built-in microphone device for use in an apparatus having a mechanism section generating internal noise inside a housing of the apparatus, the built-in microphone device comprising:

• a main microphone for picking up an external sound;
• a noise reference microphone for picking up the internal noise;
• an adaptive filter member for generating a control audio signal based on an output signal from the noise reference microphone using a filter coefficient;
• a signal subtraction section for subtracting the control audio signal generated by the adaptive filter member from an output signal from the main microphone to generate a subtraction result;
• and
• a filter coefficient update control section for updating the filter coefficient of the adaptive filter member by receiving an operation signal which is input to the mechanism section for causing the mechanism section to operate, the subtraction result generated by the signal subtraction section and an output signal from the noise reference microphone,
• wherein when a ratio of the output signal level of the noise reference microphone to the output signal level of the main microphone decreases, the filter coefficient update control section decelerates the updating of the filter coefficient, and when a ratio of the output signal level of the noise reference microphone to the output signal level of the main microphone increases, the filter coefficient update control section accelerates the updating of the filter coefficient;
• and
• when the built-in microphone device is in a wait state of recording and the output signal level from the main microphone is excessively low, the mechanism section is operated to generate noise, and said filter coefficient update section updates the filter coefficient of the adaptive filter member by receiving (1) an operations signal which is input to the mechanism section for causing said mechanism section to operate, (2) the subtraction result generated by the subtraction section and (3) an output signal from the noise reference microphone.