A noise reduction device includes a processor that converts a noise signal collected by a microphone disposed in a control space into a noise signal in a frequency domain, a storage that stores the converted noise signal in the frequency domain as a reference signal, and a signal generator that generates a noise reduction signal for reducing the noise signal collected by the microphone at a control position of the control space. The processor determines whether or not the noise signal is non-stationary noise based on a frequency characteristic of the converted noise signal in the frequency domain and a frequency characteristic of the reference signal. When it is determined that the noise signal is the non-stationary noise, the processor controls the signal generator so as to cancel generation of the noise reduction signal.

A noise reduction device includes a processor that converts a noise signal collected by a microphone disposed in a control space into a noise signal in a frequency domain, a storage that stores the converted noise signal in the frequency domain as a reference signal, and a signal generator that generates a noise reduction signal for reducing the noise signal collected by the microphone at a control position of the control space. The processor determines whether or not the noise signal is non-stationary noise based on a frequency characteristic of the converted noise signal in the frequency domain and a frequency characteristic of the reference signal. When it is determined that the noise signal is the non-stationary noise, the processor controls the signal generator so as to cancel generation of the noise reduction signal.

A double talk detection method, a double talk detection apparatus and an echo cancellation system are provided. The double talk detection method comprises: determining, according to an energy ratio between a far-end digital voice signal and a near-end digital voice signal, and a frequency coherence value between the near-end digital voice signal and the far-end digital voice signal, whether a near-end speaker's digital voice signal is present in the near-end digital voice signal. The double talk detection method avoids missing detection and false detection, improves the accuracy of double talk detection, cancels the echo in the near-end voice signal thoroughly when applied in the field of echo cancellation, and improves the communication experience of both talk parties.

A double talk detection method, a double talk detection apparatus and an echo cancellation system are provided. The double talk detection method comprises: determining, according to an energy ratio between a far-end digital voice signal and a near-end digital voice signal, and a frequency coherence value between the near-end digital voice signal and the far-end digital voice signal, whether a near-end speaker's digital voice signal is present in the near-end digital voice signal. The double talk detection method avoids missing detection and false detection, improves the accuracy of double talk detection, cancels the echo in the near-end voice signal thoroughly when applied in the field of echo cancellation, and improves the communication experience of both talk parties.

Systems and methods for operating a multi-channel intercom system for audio communications between users, with reduced crosstalk, are disclosed. Exemplary implementations may: receive, by a first user station, a modulation carrier signal; capture a first audio signal from a first user, wherein the first audio signal has a first phase; at a rate based on the modulation carrier signal, invert the first phase of the first audio signal to generate a phase-flipped audio signal; transfer the phase-flipped audio signal to a second user station; at a second rate based on the modulation carrier signal, invert a phase of the phase-flipped audio signal to generate an intermediate audio signal; and present a second audio signal based on the intermediate audio signal to the second user.

Systems and methods for operating a multi-channel intercom system for audio communications between users, with reduced crosstalk, are disclosed. Exemplary implementations may: receive, by a first user station, a modulation carrier signal; capture a first audio signal from a first user, wherein the first audio signal has a first phase; at a rate based on the modulation carrier signal, invert the first phase of the first audio signal to generate a phase-flipped audio signal; transfer the phase-flipped audio signal to a second user station; at a second rate based on the modulation carrier signal, invert a phase of the phase-flipped audio signal to generate an intermediate audio signal; and present a second audio signal based on the intermediate audio signal to the second user.

A gain control system for controlling gain applied to an audio signal includes a power estimator configured to estimate the power of a digital signal derived from the audio signal, a digital gain estimator configured to determine, in dependence on the estimated power, a digital gain which would modify the power of the digital signal so as to reach a target power level, and a gain controller configured to adjust an analogue gain applied to the audio signal in dependence on the determined digital gain.

A gain control system for controlling gain applied to an audio signal includes a power estimator configured to estimate the power of a digital signal derived from the audio signal, a digital gain estimator configured to determine, in dependence on the estimated power, a digital gain which would modify the power of the digital signal so as to reach a target power level, and a gain controller configured to adjust an analogue gain applied to the audio signal in dependence on the determined digital gain.

A method includes receiving a microphone audio signal and a playout audio signal, and determining a frequency representation of the microphone audio signal and a frequency representation of the playout audio signal. For each frequency representation, the method also includes determining features based on the frequency representation. Each feature corresponds to a pair of frequencies of the frequency representation and a period of time between the pair of frequencies. The method also includes determining that a match occurs between a first feature based on the frequency representation of the microphone audio signal and a second feature based on the frequency representation of the playout audio signal, and determining that a delay value between the first feature and the second feature corresponds to an echo within the microphone audio signal.

An acoustic sensor unit for an echo-based environment detection. The acoustic sensor unit includes a transmission unit, which is set up to emit an acoustic signal, a communications interface, and a control electronics, which is set up to output a signal via the communications interface in order to transmit information to a further acoustic sensor unit and to receive a signal from the further acoustic sensor unit via the communications interface. The acoustic sensor units are connected to one another via a bus or a network node and to a central control unit.