Microphone circuits having adjustable directivity patterns for reducing loudspeaker feedback and methods of operating the same

A microphone circuit comprising:

• a first microphone that is configured to generate a first microphone signal, the first microphone signal including a contribution associated with an output signal that is generated by a loudspeaker in response to an input signal;
• a second microphone that is configured to generate a second microphone signal, the second microphone signal including a contribution associated with the output signal from the loudspeaker;
• an adjustable delay unit that is configured to adjustably delay the second microphone signal by a delay value;
• and
• a combiner that is configured to combine the delayed second microphone signal and the first microphone signal to provide a combined microphone signal, and wherein the adjustable delay unit is further configured to adjust the delay value so as to reduce at least a portion of a contribution to the combined microphone signal associated with the output signal from the loudspeaker, wherein the adjustable delay unit is further configured to sense the input signal to the loudspeaker, and to remove at least a portion of the sensed input signal from the combined microphone signal to provide a difference signal, and to adjust the delay value based on the difference signal.

A computer program product configured to operate a microphone device, comprising:

• a computer readable storage medium having computer readable program code embodied therein, the computer readable program code comprising:
• computer readable program code for adjustably delaying a second microphone signal from a second microphone by a delay value;
• computer readable program code for combining the delayed second microphone signal with a first microphone signal from a first microphone to provide a combined microphone signal, the first and second microphone signals including contributions associated with an output signal that is generated by a loudspeaker in response to an input signal;
• computer readable program code for adjusting the delay value so as to reduce at least a portion of a contribution to the combined microphone signal associated with the output signal from the loudspeaker;
• and
• computer readable program code for adjusting the delay value based on the input signal to the loudspeaker and the combined microphone signal by removing at least a portion of the input signal to the loudspeaker from the combined microphone signal to provide a difference signal, and adjusting the delay value based on the difference signal.