Abstract: This disclosure provides methods, devices, and systems for active noise control (ANC). The present implementations more specifically relate to filter adaptation techniques for recursively training an infinite impulse response (IIR) filter to convert a reference audio signal to an anti-noise signal. In some aspects, an ANC system may record, via a feedforward microphone, a reference audio signal representing external noise, and may further record, via a feedback microphone, an error signal representing residual noise resulting from passive attenuation of the external noise via a primary path between the microphones. The ANC system may further estimate an IIR filter that converts the reference audio signal to the error signal based on a secondary path. In some implementations, the ANC system may recursively update the IIR filter coefficients based, at least in part, on the coefficients associated with previous frames of the reference audio signal and the error signal.

Abstract: This disclosure provides methods, devices, and systems for active noise control (ANC). The present implementations more specifically relate to filter adaptation techniques for recursively training an infinite impulse response (IIR) filter to convert a reference audio signal to an anti-noise signal. In some aspects, an ANC system may record, via a feedforward microphone, a reference audio signal representing external noise, and may further record, via a feedback microphone, an error signal representing residual noise resulting from passive attenuation of the external noise via a primary path between the microphones. The ANC system may further estimate an IIR filter that converts the reference audio signal to the error signal based on a secondary path. In some implementations, the ANC system may recursively update the IIR filter coefficients based, at least in part, on the coefficients associated with previous frames of the reference audio signal and the error signal.

Abstract: A method of using a dual-port measurement system to measure acoustic impedance is used to measure an acoustic impedance Z of a tested object. The tested object includes an input end and an output end opposite to the input end. The dual-port measurement system comprises a first impedance tube and a second impedance tube. The first impedance tube includes a first inlet where a plane wave of a sound source is input, and a first outlet connected with the input end. The second impedance tube includes a second inlet connected with the output end, and a second outlet where the plane wave is output. The method uses the dual-port measurement system and a two-boundary method to obtain the acoustic impedances Z, whereby the dual-port measurement system is conveniently applied to various fields, such as the design of earphones, muffler tubes, sound absorption materials, and artificial ears.

Abstract: An audio playback device is provided. The audio playback device includes a magnetic module, an annular armature, a coil module and a diaphragm. The magnetic module includes a magnetic source and two yokes each connected to one of two magnetic poles generated by the magnetic source and extends to form a magnetic field. The annular armature includes a first, a second, a third and a fourth arms that form a hollow area. At least part of the first arm is located in the magnetic area. The coil module is winded on the second arm and generates two varying electro-magnetic poles according to an alternating current data signal. The annular armature vibrates according to a relation of the two varying electro-magnetic poles and the magnetic field. The diaphragm is connected to the annular armature through a driving rod to vibrate according to the annular armature to generate a sound wave.

Abstract: A method of using a dual-port measurement system to measure acoustic impedance is used to measure an acoustic impedance Z of a tested object. The tested object includes an input end and an output end opposite to the input end. The dual-port measurement system comprises a first impedance tube and a second impedance tube. The first impedance tube includes a first inlet where a plane wave of a sound source is input, and a first outlet connected with the input end. The second impedance tube includes a second inlet connected with the output end, and a second outlet where the plane wave is output. The method uses the dual-port measurement system and a two-boundary method to obtain the acoustic impedances Z, whereby the dual-port measurement system is conveniently applied to various fields, such as the design of earphones, muffler tubes, sound absorption materials, and artificial ears.

Abstract: A method for visualizing sound source energy distribution in an echoic environment comprises steps: arranging in an echoic environment a plurality of arrayed sound pickup units, wherein each sound pickup unit includes at least two microphones separated by a directive distance enabling the sound pickup unit to have a primary pickup direction; disposing the sound pickup units with the primary pickup directions thereof pointing toward a sound source in the echoic environment, and measuring the sound source by the sound pickup units to obtain a sound source-related parameter; substituting the directive distance and the parameter into an algorithm to make the parameter have directivity; and then substituting the parameter into an ESM algorithm to establish a sound source energy distribution profile. Thereby, the method can measure a sound source in a specified direction in an echoic environment and establish a visualized sound source energy distribution profile.

Abstract: A miniature electronic shotgun microphone, which is used to receive a sound source from a specified direction, comprises a pick-up member, an A/D (Analog/Digital) conversion unit, and a digital signal processor. The pick-up member includes a first pick-up unit, a second pick-up unit separated from the first pick-up unit by a first distance, and a third pick-up unit separated from the second pick-up unit by a second distance; the first distance is greater than the second distance. The first pick-up unit, the second pick-up unit and the third pick-up unit respectively receive the sound source and output an analog signal. The A/D conversion unit and the digital signal processor process the analog signals, and convert them into a directional digital acoustic signal. Thus, the directional digital acoustic signal has a maximum pick-up frequency. Thereby is decreased grating lobes and spatial aliasing.

Abstract: An audio playback device is provided. The audio playback device includes a magnetic module, an annular armature, a coil module and a diaphragm. The magnetic module includes a magnetic source and two yokes each connected to one of two magnetic poles generated by the magnetic source and extends to form a magnetic field. The annular armature includes a first, a second, a third and a fourth arms that form a hollow area. At least part of the first arm is located in the magnetic area. The coil module is winded on the second arm and generates two varying electro-magnetic poles according to an alternating current data signal. The annular armature vibrates according to a relation of the two varying electro-magnetic poles and the magnetic field. The diaphragm is connected to the annular armature through a driving rod to vibrate according to the annular armature to generate a sound wave.

Abstract: A miniature electronic shotgun microphone, which is used to receive a sound source from a specified direction, comprises a pick-up member, an A/D (Analog/Digital) conversion unit, and a digital signal processor. The pick-up member includes a first pick-up unit, a second pick-up unit separated from the first pick-up unit by a first distance, and a third pick-up unit separated from the second pick-up unit by a second distance; the first distance is greater than the second distance. The first pick-up unit, the second pick-up unit and the third pick-up unit respectively receive the sound source and output an analog signal. The A/D conversion unit and the digital signal processor process the analog signals, and convert them into a directional digital acoustic signal. Thus, the directional digital acoustic signal has a maximum pick-up frequency. Thereby is decreased grating lobes and spatial aliasing.

Abstract: A method for visualizing sound source energy distribution in an echoic environment comprises steps: arranging in an echoic environment a plurality of arrayed sound pickup units, wherein each sound pickup unit includes at least two microphones separated by a directive distance enabling the sound pickup unit to have a primary pickup direction; disposing the sound pickup units with the primary pickup directions thereof pointing toward a sound source in the echoic environment, and measuring the sound source by the sound pickup units to obtain a sound source-related parameter; substituting the directive distance and the parameter into an algorithm to make the parameter have directivity; and then substituting the parameter into an ESM algorithm to establish a sound source energy distribution profile. Thereby, the method can measure a sound source in a specified direction in an echoic environment and establish a visualized sound source energy distribution profile.