The present teachings relate to an electronic device comprising: a first module for generating an audio signal; a second module for generating an ultrasonic signal; a mixer for generating a combined signal; a transmitter for outputting an acoustic signal dependent upon the combined signal; and, a processing means for controlling the ultrasonic signal; wherein, in response to receiving a first instruction signal for initiating the ultrasonic signal, the processing means is configured to increase the amount of the ultrasonic signal in the combined signal from an essentially zero value to a predetermined value over a predetermined enable time-period. The present teachings also relate to an electronic device configured to decrease the amount of the ultrasonic signal in the combined signal from an essentially zero value to a predetermined value over a predetermined disable time-period, and to an electronic device configured to remove the audio signal from the combined signal whilst preventing pop-noise, and to an electronic device capable of replacing the ultrasonic signal whilst minimizing the processing time. The present teachings further relate to a method for reducing the occurrence of pop noise in an acoustic signal associated with: initiating the ultrasonic signal in the combined signal, terminating the ultrasonic signal in the combined signal, terminating the audio signal in the combined signal, and replacing the ultrasonic signal in the combined signal. The present teachings also relate to a computer software product for implementing any of the method steps disclosed herein, and to a computer storage medium storing the computer software herein disclosed.

A method for eliminating unstable noise is provided and applicable to a sound recording device and implemented by a codec. The method includes: activating the sound recording device to start recording; setting a suppression duration and a cutoff frequency switching duration according to unstable noise and a DC offset value of the sound recording device; processing a front-end audio of a recorded sound by a filter having a first cutoff frequency to make the unstable noise in the front-end audio quickly converge, and outputting a filtered audio signal; suppressing the filtered audio signal according to the suppression duration to eliminate the unstable noise; and adjusting the first cutoff frequency of the filter to a second cutoff frequency according to the cutoff frequency switching duration, where the first cutoff frequency is greater than the second cutoff frequency. A device for eliminating unstable noise is also provided.

A system for controlling the gain of an input signal in an audio signal amplifier. The system includes a user-operable gain control, and analog and digital circuit elements that together are configured to modify the gain of the input signal in response to the user-operable gain control.

A method of operating a headphone configured to be removed from and placed in close proximity to a user's ear can include generating an input signal by an input signal generating device. The method can also include determining whether an insertion event has occurred based on the generated input signal and causing the headphone to operate in 5 a low power mode responsive to an absence of an insertion event determination after a first period of time. The method can also include causing the headphone to operate in an ultra-low power mode responsive to the absence of an insertion event determination after a second period of time that occurs after the first period of time, the ultra-low power mode having a lower power consumption than the low power mode.

Embodiments described herein provide for detecting presence of an object in proximity to a playback device and responsively performing one or more operations. In an example implementation, a playback device detects, via a proximity detector of the playback device, presence of an object in proximity to the playback device. In response to detecting the presence of the object, the playback device performs one or more operations.

A digital signal generator apparatus and method is described. The digital signal generator includes a counter, an integrator and a comparator. The counter counts up or down from an initial counter value dependent on a counter control input. The comparator has a first input coupled to the counter output, a threshold input and a comparator output coupled to the counter control input. The integrator has an input coupled to the counter output and an output coupled to the digital signal generator output. The digital signal generator determines the count direction after the initial direction dependent on the comparison between a threshold value applied to the threshold input and the counter output value. The digital signal generator may implement the generation of a waveform having an approximation to a raised cosine function. The generated waveform may be used for audio artefact reduction in an audio amplifier during mute or unmute operations or during power up power down operations.

A method may be provided for powering up or down a playback path comprising a digital-to-analog converter (DAC) for generating a non-ground-centered analog intermediate voltage centered at a common-mode voltage and coupled to a driver for generating a ground-centered playback path output voltage at an output of the driver wherein the output of the driver is clamped via a finite impedance to a ground voltage. The method may include transitioning continuously or in a plurality of discrete steps the analog intermediate voltage from an initial voltage to the common-mode voltage such that the transitioning is substantially inaudible at the output of the driver. A method for operating an output clamp of an output driver stage of a playback path may include transitioning continuously or in a plurality of discrete steps an impedance of the output clamp in order to match an output offset of the output driver stage in order to minimize audio artifacts appearing at an output of the output driver stage.

A headphone driver includes a pre-main amplifier and a main amplifier. The pre-main amplifier receives an input signal from first and second node and outputs the input signal to a third node. The main amplifier is between the third node and a fourth node. A first switch is between the fourth node and a fifth node. A second switch is between the fourth node and a sixth node. A third switch is between the fourth node and a seventh node. A fourth switch is between the fifth and seventh nodes. A fifth switch is between the first and fifth nodes. A capacitor is between the third and fifth nodes. A first feedback resistor is between the first and seventh nodes. A second feedback resistor is between the second and sixth nodes, and the sixth and seventh nodes are connected to a speaker.

A receiving device having a wireless transmission circuit arranged to form a logical communications link between the wireless transmission circuit and an audio output device. The wireless transmission circuit is arranged to communicate audio data to the audio output device via the logical communications link. A wireless reception circuit is arranged to receive user commands, and a first logic circuit is arranged to identify a mute command received via the wireless reception circuit. A second logic circuit is arranged to mute the audio data from transmission to the audio output device while maintaining the logical communications link.

A close-down pop reduction system and a method for close-down pop reduction in an audio amplifier assembly are disclosed. The switching power conversion system comprises a forward path having a compensator and a switching power stage and a signal path from an output of a comparator in the switching power stage to a sequence control unit. The signal path includes a close-down timing circuit configured to provide a timing signal. The sequence control unit is configured to eliminate the input signal, increase the switch frequency of the close-down pop reduction system and disable the switching power stage at a moment in time within a PWM pulse of the switching power stage. Hereby, it is e.g. possible to minimize the audible pop during close-down of audio amplifier assemblies.