Embodiments can provide individualized controlling of noise injection during startup of a crystal oscillator. In some embodiments, a simple learning block can be placed in parallel to a oscillator circuit to control noise injection during the startup of the crystal oscillator. The learning block can be configured to control the noise injection during the startup of the crystal oscillator by determining whether the crystal oscillator has been stabilized. In some embodiments, an adjustment block may be employed to adjust the count determined by the learning block based on one or more measured characteristics of the crystal oscillator during a startup of the crystal oscillator. In some embodiments, a simple block that creates a negative capacitance can be configured in parallel to the crystal oscillator.

A method of determining an audio controller for a headphone that is configured to use an acoustic transducer to develop sound that is delivered to an ear of a user and that includes a feedback microphone that is configured to sense sound developed by the acoustic transducer, and a related computer program product and system. A first audio transfer function between the acoustic transducer and the feedback microphone is measured. A second audio transfer function between the acoustic transducer and the feedback microphone with a feedback controller applied is determined. The audio controller is calculated based on both the first audio transfer function and the second audio transfer function.

This application provides a noise generation circuit, a self-checking circuit, an AFCI, and a photovoltaic power generation system. The noise generation circuit includes a power switch module, a noise generator, and a capacitor, where the noise generator is connected to both the power switch module and the capacitor; the power switch module is configured to control, according to a self-checking instruction, whether the noise generator generates a noise signal; and the capacitor is configured to filter out a direct current component in the noise signal when the noise generator generates the noise signal. According to the noise generation circuit, the self-checking circuit, the AFCI, and the photovoltaic power generation system that are provided in this application, no noise signal is generated in a non self-checking time, thereby ensuring normal working of the AFCI and the photovoltaic inverter.

Apparatus and methods for distributing spurious tones through the frequency domain are disclosed. One such apparatus can include a dithering circuit configured to generate a sequence of numbers that exhibit statistical randomness and a variable frequency circuit configured to adjust a frequency of an output based on the sequence of numbers so as to spread energy of spurious tones in a frequency response of the output to lower a noise floor. In one example, spurious tones can be reduced in a negative voltage generator of a radio frequency (RF) attenuator.

Apparatus and methods for distributing spurious tones through the frequency domain are disclosed. One such apparatus can include a dithering circuit configured to generate a sequence of numbers that exhibit statistical randomness and a variable frequency circuit configured to adjust a frequency of an output based on the sequence of numbers so as to spread energy of spurious tones in a frequency response of the output to lower a noise floor. In one example, spurious tones can be reduced in a negative voltage generator of a radio frequency (RF) attenuator.

A system has multiple audio-enabled devices that communicate with one another over an open microphone mode of communication. When a user says a trigger word, the nearest device validates the trigger word and opens a communication channel with another device. As the user talks, the device receives the speech and generates an audio signal representation that includes the user speech and may additionally include other background or interfering sound from the environment. The device transmits the audio signal to the other device as part of a conversation, while continually analyzing the audio signal to detect when the user stops talking. This analysis may include watching for a lack of speech in the audio signal for a period of time, or an abrupt change in context of the speech (indicating the speech is from another source), or canceling noise or other interfering sound to isolate whether the user is still speaking. Once the device confirms that the user has stopped talking, the device transitions from a transmission mode to a reception mode to await a reply in the conversation.

A clock generator including a phase frequency detector configured to compare a phase and a frequency of a reference clock signal with a phase and a frequency of a first output clock signal and generate a detection signal based on a difference in the phases and frequencies of the clock signals; a loop filter configured to generate a first control voltage signal based on the detection signal; a first voltage controlled oscillator configured to generate and output a first output clock signal based on the first control voltage signal, a modulation filter configured to generate a modulation voltage signal based on the reference clock signal and generate a second control voltage signal by combining the modulation voltage signal and the first control voltage signal, and a second voltage controlled oscillator configured to generate and output a second output clock signal based on the second control voltage signal is provided.

A clock generator including a phase frequency detector configured to compare a phase and a frequency of a reference clock signal with a phase and a frequency of a first output clock signal and generate a detection signal based on a difference in the phases and frequencies of the clock signals; a loop filter configured to generate a first control voltage signal based on the detection signal; a first voltage controlled oscillator configured to generate and output a first output clock signal based on the first control voltage signal, a modulation filter configured to generate a modulation voltage signal based on the reference clock signal and generate a second control voltage signal by combining the modulation voltage signal and the first control voltage signal, and a second voltage controlled oscillator configured to generate and output a second output clock signal based on the second control voltage signal is provided.

An earpiece of a headset uses a first signal and a second signal received from an in-ear microphone and an outside microphone, respectively, to enhance microphone signals. The in-ear microphone is positioned at a proximal side of the earpiece with respect to an ear canal of a user, and the outside microphone is positioned at a distal side of the earpiece with respect to the ear canal. A processing unit includes a filter, which digitally filters out in-ear noise from the first signal using the second signal as a reference to produce a de-noised signal to thereby enhance the microphone signals.

A noise extracting device includes first and second microphones that are provided at spatially different positions and pick up sounds, a first noise signal extractor that extracts a first noise signal included in a first signal obtained by subjecting output signals of the first and second microphones to directionality combining, a second noise signal extractor that obtains a second noise signal included in a second signal different from the first signal in a condition of the directionality combining, and a noise signal separator that separates the first and second noise signals into individual noise signals indicating noises generated in the respective first and second microphones.