An active noise cancelling device including a sensor configured to convert acoustic signals into first audio signals and a speaker acoustically coupled to the sensor A control stage is configured to control the speaker based on the first audio signals to cause the speaker to produce cancelling acoustic waves that tend to suppress acoustic noise components in the acoustic signals. The control stage includes sigma-delta modulator digital filters.

A digital circuit arrangement for an ambient noise-reduction system affording a higher degree of noise reduction than has hitherto been possible. The arrangement converts the analog signals into N-bit digital signals at sample rate f.sub.0, and then subjects the converted signals to digital filtering. The value of N in some embodiments is 1 but, in any event, is no greater than 8, and f.sub.0 may be 64 times the Nyquist sampling rate but, in any event, is substantially greater than the Nyquist sampling rate. This permits digital processing to be used without incurring group delay problems that rule out the use of conventional digital processing in this context. Furthermore, adjustment of the group delay can readily be achieved, in units of a fraction of a micro-second, providing the ability to fine tune the group delay for feed forward applications.

Systems and methods for low latency adaptive noise cancellation include an audio sensor to sense environmental noise and generate a noise signal, an audio processing path to receive an audio signal, process the audio signal through an interpolation filter, and generate a primary audio signal having a first sample frequency, an adaptive noise cancellation processor to receive the noise signal and generate an anti-noise signal, a direct interpolator to receive the anti-noise signal and generate an anti-noise signal having the first sample frequency, and a limiter to provide clipping to reduce a number of bits in the anti-noise signal, an adder operable to combine the primary audio signal and the anti-noise signal and generate a combined output signal, and a low latency filter to process the combined output signal.

An earphone noise reduction method and apparatus, which are applicable to the technical field of wearable devices. The earphone noise reduction method can include collecting, using an earphone microphone, a noise signal of an environment where the earphone microphone is placed. The method can also include transmitting the noise signal to a connected terminal or transmitting a noise value corresponding to the noise signal to the connected terminal. The method can further include receiving a judgement result returned by the terminal, and enabling a noise reduction function or disabling the noise reduction function according to the judgement result. Embodiments of the present disclosure can be realized without keys or toggle switches for noise reduction adjustment on earphones. Embodiments of the present disclosure are capable of automatic noise reduction, thereby improving the integration degree of the earphones and also enhancing the battery life of the earphones.

Audio recorded by a cellphone or other portable recording device (e.g., audio recorded as part of a video recording of a play or other event) is often of low quality, due to the limitations of the portable recording device. Multiple audio recordings, made during the same period of time and near the same location, can be combined to generate an improved-quality audio recording of an event. The audio recordings may be accessible to a server that selects the audio recordings and performs the combination. To protect the privacy of persons whose audio is used, more than a minimum number of recordings could be combined and/or no more than a threshold amount of any one recording could be used to generate a combined recording. Additionally, a provided clean recording could include more than a threshold amount of the audio provided by a user or device that requests such a clean recording.

A method may include adaptively generating an anti-noise signal from filtering a reference microphone signal with an adaptive filter in conformity with an error microphone signal and the reference microphone signal. The method may also include adjusting the response of the adaptive filter by combining injected noise with the reference microphone signal and receiving the injected noise by a copy of the adaptive filter so that the response of the copy is controlled by the adaptive filter adapting to cancel a combination of the ambient audio sounds and the injected noise and controlling the response of the adaptive filter with the coefficients adapted in the copy, whereby the injected noise is not present in the anti-noise signal and wherein each of a sample rate of the copy and a rate of adapting of the adaptive filter is significantly less than a sample rate of the adaptive filter.

An active noise cancellation system for canceling noises within a predetermined bandwidth includes an analog-to-digital converter, a programmable noise-cancellation module, a first interpolation filter and a digital-to-analog converter. The analog-to-digital converter receives a first audio signal, and converts the first audio signal from an analog signal to a digital signal. The programmable noise-cancellation processes the first audio signal to generate a noise cancellation signal. The first interpolation filter receives a second audio signal and filters the second audio signal. The noise cancellation signal and the filtered second audio signal are integrated by an adder as a third audio signal, and then the digital-to-analog converter converts the third audio signal from a digital signal to an analog signal.

An active noise cancellation system for canceling noises within a predetermined bandwidth includes an analog-to-digital converter, a programmable noise-cancellation module, a first interpolation filter and a digital-to-analog converter. The analog-to-digital converter receives a first audio signal, and converts the first audio signal from an analog signal to a digital signal. The programmable noise-cancellation processes the first audio signal to generate a noise cancellation signal. The first interpolation filter receives a second audio signal and filters the second audio signal. The noise cancellation signal and the filtered second audio signal are integrated by an adder as a third audio signal, and then the digital-to-analog converter converts the third audio signal from a digital signal to an analog signal.

A maximum noise suppression level (G.sub.min) is not a single constant value for an entire frequency range, but is allowed to vary across frequencies. The amount of variation is dynamically computed based on the input noise characteristics. For example, if there is excess noise in the lower frequency region, the maximum noise suppression level in that region will increase to suppress the noise in that frequency region. This feature can be enabled all the time, and will be active when the input conditions warrant extra noise suppression in a particular frequency region. Thus, the effort involved in manually tuning an audio system (e.g., hands-free telephony, voice-controlled automotive head unit, etc.) can be significantly reduced or eliminated.

A simulation system and method for simulating a noise environment of a vehicle includes a memory configured to store a reference sample signal and a noise sample signal, a control unit electrically connected to the memory and configured to generate a reference signal based on the reference sample signal, generate a noise signal based on the noise sample signal, and transmit the reference signal to a noise control system, and a speaker electrically connected to the control unit and configured to convert the noise signal into a sound wave and output the sound wave.