Passive balancing of electroacoustic transducers for detection of external sound

A method of using electroacoustic transducers to detect environmental sound not produced by the electroacoustic transducers, comprising:

• receiving a monophonic audio signal;
• providing the monophonic audio signal to a first voice coil and a second voice coil, the first voice coil driving a first sound-reproducing diaphragm, and the second voice coil having an opposite polarity from the first voice coil and driving a second sound-reproducing diaphragm;
• and
• receiving at a common electrical point coupled to the first and second voice coils the monophonic audio signal from the first voice coil and the monophonic audio signal from the second voice coil having the opposite polarity from the first voice coil thereby causing the monophonic audio signal from the first voice coil and the monophonic audio signal from the second voice coil to cancel out thereby creating a residual output signal that represents the environmental sound received by the first and second diaphragms.

A circuit for using electroacoustic transducers to detect an environmental sound received by but not produced by the electroacoustic transducers, comprising:

• a first amplifier configured to provide a monophonic audio signal to a first voice coil, the first voice coil driving a first diaphragm;
• a second amplifier configured to invert the monophonic audio signal and provide the inverted monophonic audio signal to a second voice coil, the second voice coil driving a second diaphragm;
• and
• an amplifier coupled to a common electrical point of the first and second voice coils and configured to receive the monophonic audio signal and the inverted monophonic audio signal, causing the monophonic audio signal and the inverted monophonic audio signal to cancel out thereby creating a residual output signal that represents the environmental sound received by the first and second diaphragms.

A circuit for using electroacoustic transducers to detect an environmental sound received by but not produced by the electroacoustic transducers, comprising:

• a first amplifier configured to provide a monophonic audio signal to a first voice coil, the first voice coil driving a first diaphragm;
• a second amplifier configured to provide the monophonic audio signal to a second voice coil, the second voice coil having an opposite polarity from the first voice coil and driving a second diaphragm;
• and
• an amplifier coupled to a common electrical point of the first and second voice coils, causing the monophonic audio signal from the first voice coil and the monophonic audio signal from the second voice coil to cancel out thereby creating a residual output signal that represents the environmental sound received by the first and second diaphragms.