Abstract: Some embodiments of the present invention provide a system that attenuates noise from a fan exhaust of a computer system. During operation, the system monitors the noise from the fan exhaust and calculates a frequency spectrum of the noise from the monitored noise. Next, the system generates an antiphase spectrum from the frequency spectrum and generates a flow of air which exhibits a property of the antiphase spectrum. Finally, the system directs the flow of air into the fan exhaust so that the noise is attenuated by a reduction of turbulence in the fan exhaust by the flow of air.

Abstract: In an active noise cancellation system having an adaptive filter that outputs a control signal, first and second speakers that emit a canceling signal generated based on the control signal, a microphone that detects an error signal, a correction filter that corrects the base signal by a correction value to generate a reference signal and a filter coefficient updater that successively updates the adaptive filter coefficient based on the error signal and reference signal such that the error signal is minimized, the correction value of the correction filter is set to a sum obtained by adding the transfer characteristic from the first speaker to the microphone, and a product obtained by multiplying the transfer characteristic from the second speaker to the microphone by the prescribed value, thereby enabling to reduce the number of microphones and avoid the increase in parts, the amount of work to provide complicated wiring to the microphones, and the computational load involved in updating the adaptive filter co

Abstract: A signal processing circuit is intended for use in a noise reduction system, which produces a target filter characteristic that would achieve optimal noise cancellation, the target filter characteristic including a resonant peak at a first frequency. The signal processing circuit comprises an analogue filter, which has an amplitude response that has a peak or trough at a centre frequency, and has a phase response that switches polarity at the centre frequency and tends to zero with increase or reduction in frequency away from the centre frequency. The centre frequency in the amplitude response is substantially equal to the first frequency. The analogue filter may be in the form of a series inductive-capacitive-resistive circuit, where the inductive component is in the form of a gyrator.

Abstract: The invention regards a method for noise reduction in an audio device whereby an electrical and/or digital signal which represents sound is routed simultaneously through:—a signal analysis path, and—a signal processing path wherein the signal amplification is individually controllable in specific frequency bands by attenuation values derived from the signal analysis path, whereby the signal in the signal analysis path is routed simultaneously through:—a first detector which identifies the presence of speech indicators in the overall signal, and—a second detector which in a predefined number of frequency bands detects the modulation amplitude, and—where attenuation values in each of the predefined frequency bands are calculated based on the combined results of the first detector and the modulation amplitude in the specific frequency band detected by the second detector,—where the attenuation values in the predefined number of frequency bands are routed to the signal processing path in order to attenuate the si

Abstract: A method and implementation for detecting and characterizing audible transients in noise includes placing a microphone in a desired location, producing a microphone signal wherein the microphone signal is indicative of the acoustic environment, processing the microphone signal to estimate the acoustic activity that takes place in the human auditory system in response to the acoustic environment, producing an excitation signal indicative of the estimated acoustic activity, processing the excitation signal to identify each impulsive sound frequency-dependent activity as a function of time, producing a detection signal indicative of audible impulse sounds, processing the detection signal to identify an audible impulsive sound, and characterizing each impulsive sound.

Abstract: Disclosed herein is a digital filter circuit for producing a noise reduction signal for reducing noise based on a noise signal outputted from a microphone which collects the noise, including: an analog/digital conversion section; a first digital filter section; an arithmetic operation processing section; a second digital filter section; and a digital/analog conversion section. The first digital filter section and/or the second digital filter section are configured such that a predetermined attenuation amount is obtained within a predetermined range in the proximity of a sampling frequency around the sampling frequency.

Abstract: A system and method of reducing noise in an enclosure is disclosed. The method includes receiving at least one reference signal; receiving pressure signals from no more than two substantially orthogonally placed pairs of acoustic sensors, where one pair of acoustic sensors is in the x-direction and one pair of acoustic sensors is in the y-direction, and where the acoustic sensors are placed in a plane which is substantially parallel and in proximity to an inner surface of the enclosure; using the pressure signals and the reference signal to generate an output signal to minimize energy density at a location of the acoustic sensors; and sending the output signal to an acoustic actuator.

Abstract: An active noise reduction system using adaptive filters. A method of operation the active noise reduction system includes smoothing a stream of leakage factors. The frequency of a noise reduction signal may be related to the engine speed of an engine associated with the system within which the active noise reduction system is operated. The engine speed signal may be a high latency signal and may be obtained by the active noise reduction system over audio entertainment circuitry.

Abstract: A system and method for actively damping boom noise within an enclosure such as an automobile cabin. The system comprises an acoustic wave sensor, a motion sensor, an acoustic wave actuator, a first electronic feedback loop, and a second electronic feedback loop. The enclosure defines a plurality of low-frequency acoustic modes that can be induced/excited by the enclosure cavity, by the structural vibration of a panel of the enclosure, by idle engine firings, and a combination thereof. The acoustic wave actuator is substantially collocated with the acoustic wave sensor within the enclosure. The motion sensor can be secured to a panel of the enclosure.

Abstract: A multi-channel active noise control system and method of reducing tonal noise emanating from a tonal noise source are disclosed. The system may include an adaptive controller, a plurality of loudspeakers driven by the loudspeaker, one or more microphones for generating one or more error signals to feedback to the adaptive controller and optionally a reference signal source to provide the adaptive controller with frequency information associated with the tonal noise source. The system and method of the present invention are applicable to any tonal noise source, including but not limited to axial fans.

Abstract: A system for actively damping the low-frequency coloration of sound in a listening room is provided comprising an acoustic wave sensor, an acoustic wave actuator, and an electronic feedback controller. The listening room defines at least one mode of low-frequency coloration. The acoustic wave actuator is substantially collocated with the acoustic wave sensor within the listening room. The electronic feedback controller is operative to generate a signal at its output by applying a feedback controller transfer function. The feedback controller transfer function comprises a second order differential equation including a first variable representing a predetermined damping ratio and a second variable representing a tuned natural frequency and creates a 90 degree phase lead substantially at the resonant frequencies of at least one mode of low-frequency coloration. The feedback controller output signal represents a rate of change of volume velocity to be produced by the acoustic wave actuator.

Abstract: The invention provides an apparatus and related method for acoustically improving an environment. In an embodiment of the present invention, an electronic sound screening system includes a portion for receiving acoustic energy and converting it into electrical signals, a portion for performing an analysis of the electrical signals and for generating data analysis signals, a portion responsive to the data analysis signals for producing signals representing sound, and an output portion for converting the sound signals into sound.

Abstract: A system and method facilitating acoustic echo cancellation convergence detection is provided. The invention includes an acoustic echo cancellation convergence detector having a center clipping component, a convergence calculator, a convergence filter and a convergence statistic component. The invention provides for the acoustic echo cancellation convergence detector to provide an output regarding convergence of an adaptive filter based, at least in part, upon a filtered convergence statistic. Optionally, the acoustic echo cancellation convergence detector can provide an output associated with convergence history.

Abstract: The amount of data produced in the process of recording even short hearing samples by means of a monitor (1) may be considerably reduced by effecting a normalization to a range of values D and a subsequent nonlinear mapping to a second, preferably smaller range of values W. The result may be stored in an electronic memory. Further preferred measures are the spitting of the hearing samples into e.g. 6 signals each of which contains a respective frequency band of the original signal, and the conversion of the original amplitude values into energy variation values with simultaneous low pass filtering. Preferably, all cited processing steps are performed by a signal processor (9). A continuous recording time of up to 14 days by a monitor in the form of a wristwatch can thus be attained with state-of-the-art technology.

Abstract: Controlling the presentation of audio data in a communication device includes receiving a certain first signal sequence with a microphone of the communication device, saving the first signal sequence to a temporary memory of a detector unit, receiving a certain second signal sequence with the microphone, and comparing the saved first signal sequence and the received second signal sequence to each other. If the compared signal sequences correlate, the received second signal sequence is attenuated before it is expressed with a loudspeaker or transmitted from an antenna.

Abstract: A phase-locked loop (PLL) circuit generates a sine wave signal synchronized with an input signal. The sine wave signal is directly supplied to a first multiplier. The sine wave signal is also supplied to a second multiplier after shifting the phase by 90 degrees by an all-pass filter (APF). The first and second multipliers multiply the corresponding input signals by corresponding predetermined gains. An adder sums the products. Sound corresponding to the sum is produced from a speaker to a sound field. A filter-controlling unit controls the gains for the first and second multipliers, respectively, to minimize an error signal “e” for the output level of a microphone installed at a listening position.

Abstract: A noise canceling apparatus (1) comprises an amplifier (10) for amplifying a measured signal (ms) outputted from a measuring device (3), an analog filter (11), an ADC (12), a digital filter (14), a coefficient control section (13), and a data input section (15). The digital filter (14) is a notch filter for attenuating a frequency component of a quantitative signal D(n) outputted from the ADC (12) at a plurality of notches (stop bands). A transfer function of the digital filter (14) is expressed by the product of a plurality of factors each having a root that corresponds to each one of the plurality of notches. The coefficient control section (13) changes a frequency component of a root corresponding to a notch selected from the plurality of notches, and thereafter, expands in a polynomial the transfer function of the reconstructed digital filter (14). On the basis of the polynomial thereby obtained, a new series of filter coefficients is calculated.

Abstract: An analog filter is connected at the output of a D/A converter. The analog filter eliminates higher frequency components than the original basic frequencies for a digital audio system and improves the phase characteristic. The analog filter comprises a plurality of band elimination filters that have respective cutoff frequencies of integral multiples of the sampling frequency fs. An audio amplifying circuit is connected to the analog filter. Each band elimination filter eliminates side band components close to integral multiples of the sampling frequency. By such construction, the analog filter has the necessary amplitude characteristic and lessens phase shift within the basic frequency.

Abstract: The invention intends to reduce the manufacturing cost of the noise shaper for processing stereo signals, to reduce the occupancy area of the circuit, and to reduce the power consumption of the noise shaper. In order to process a serial digital stereo signal in time-sharing, the noise shaper takes on a construction including: a conversion means that converts the inputted stereo signals into a serial time-division-multiplexed signal; an integration means that applies a delta sigma modulation to an inputted signal, in which integrators for integrating the inputted signal are connected in multi-stages; and a means that outputs to separate a noise shaped signal into right and left channel signals. Here, the integration means possesses an adding means, two storage means to which an output from the adding means is inputted, and a selection means that selects in time-sharing either of the outputs from the two storage means. And, the output of the selection means is fed back to the adding means.

Abstract: A method and apparatus for actively influencing the intake noise of an internal combustion engine. The apparatus comprises a controller (7) which senses the actual noise (I) via a microphone (16) and compares the actual noise with a reference noise signal which depends on the engine speed D and at least one further engine parameter P, such as, for example, the throttle (12) position. A comparison signal V generated by comparing the actual noise to the reference noise value is used to adjust a control signal Asum, which also depends on the engine speed D. The control signal is fed to an electromechanical transducer (14) which generates a correcting noise (20) which is superimposed on the intake noise (21) to produce the resultant actual noise (22), which should correspond as closely as possible to the reference noise value.

Abstract: A system and method (and storage media) for identifying the category of the source noise and sound by using the physical factors derived from the autocorrelation function (ACF) and the interaural crosscorrelation function (IACF) which are ever changing in the time domain based on the model of human auditory brain function system. A method for evaluating a sound comprises the steps of: using the sound recorder to capture and record the acoustic signal; calculating the ACF from the acoustic signal using a CPU; calculating ACF factors extracted from the calculated ACF using the CPU; and identifying the kinds of the noise based on the ACF factors. Thereby the unknown noise source can be identified what it is (such as automobile noise, and factory noise), and can be identified its type such as type of cars or type of machines.

Abstract: A multi-channel active noise control system and method of reducing tonal noise emanating from a tonal noise source are disclosed. The system may include an adaptive controller, a plurality of loudspeakers driven by the loudspeaker, one or more microphones for generating one or more error signals to feedback to the adaptive controller and optionally a reference signal source to provide the adaptive controller with frequency information associated with the tonal noise source. The system and method of the present invention are applicable to any tonal noise source, including but not limited to axial fans.

Abstract: A phase-locked loop (PLL) circuit generates a sine wave signal synchronized with an input signal. The sine wave signal is directly supplied to a first multiplier. The sine wave signal is also supplied to a second multiplier after shifting the phase by 90 degrees by an all-pass filter (APF). The first and second multipliers multiply the corresponding input signals by corresponding predetermined gains. An adder sums the products. Sound corresponding to the sum is produced from a speaker to a sound field. A filter-controlling unit controls the gains for the first and second multipliers, respectively, to minimize an error signal “e” for the output level of a microphone installed at a listening position.

Abstract: An active noise cancellation apparatus and method for actively reducing the level of noise generated by an ambient noise source, such as a domestic appliance. This active noise cancellation apparatus has a pickup device (1, 20) to translate the noise into an electrical signal, a buffer amplifier (2, 22) to allow the distribution of those signals to a digital filter section (3) having a series of switched capacitor filters for analyzing and dividing the signal into separate harmonic signals, a dual analog delay line (4) for producing a phase shift in the signals, a summing amplifier (2,6) to recombine the signals into one signal, a power amplifier (5, 27) to drive an output loudspeaker (6, 31) which produces a phase shifted sound wave to cancel the noise generated by the ambient noise source.

Abstract: An adaptive noise rejection method and apparatus. An information signal having an information component and a repetitive noise component having a varying characteristic frequency is delayed the information signal by a reference delay time that is equal that is equal to a predetermined number of periods of the characteristic frequency to form a delayed information signal. The delayed information signal is subtracted from the information signal to form a processed information signal in which the information component is substantial and the noise component is negligible. The amplitude of the noise component of the processed information signal is constantly monitored. The delay of the information signal is varied as the characteristic frequency of the noise component changes so as to maintain the amplitude of the noise component of the processed information signal at a predetermined level.

Abstract: A system for identifying a model of an acoustic system in the presence of an external noise signal is disclosed. The system includes an acoustic actuator for generating controlled sound within the acoustic system. A sensor receives the controlled sound and the external noise signal and produces a sensed signal. A control system generates a control signal in response to an error signal. The control system includes a system model for generating an estimated response signal. The control system also generates the error signal representing the difference between the sensed signal and the estimated response signal. A masking threshold generator receives the sensed signal and the error signal and produces spectral shaping parameters. A shaped signal generator for receives the spectral shaping parameters and produces a test signal which is provided as an input to the control system.

Abstract: A method and system for removing acoustic noise removal from human speech is described. Acoustic noise is removed regardless of noise type, amplitude, or orientation. The system includes a processor coupled among microphones and a voice activation detection (“VAD”) element. The processor executes denoising algorithms that generate transfer functions. The processor receives acoustic data from the microphones and data from the VAD. The processor generates various transfer functions when the VAD indicates voicing activity and when the VAD indicates no voicing activity. The transfer functions are used to generate a denoised data stream.

Abstract: In an active noise control method of the present invention, a noise detection signal from a noise referring microphone which detects ambient noise is inputted into noise processing units of different types to produce noise silencing signals. A selected noise silencing signal is inputted into a receiver or a speaker together with a reception signal via an adder, so that a regenerated tone from the noise silencing signal silences the ambient noise, When a nonconformance detecting unit judges that the selected noise silencing signal exceeds a predetermined range, the corresponding noise processing unit is judged to be incompatible, and a switch control unit controls a switch to select another one of the noise processing units.

Abstract: noise extraction method in which an environmental input which includes a noise indicia is selectively modified in accordance with an algorithm that includes one or more factors representing time response, amplitude of response, and error correction. The algorithm may also include thresholding delay or convergence, among other techniques.

Abstract: A noise suppressor for reducing propagation of a floor impact noise generated in an upper story to a lower story in a multi-storied building is disclosed. A reference sensor set at a position between a floor of the upper story and a ceiling of the lower story detects a floor impact noise generated in the upper story and converts the noise to an electric signal. This signal is computed and processed by a control unit and transmitted to a speaker located at a position lower than the reference sensor. The speaker emitts a sound wave interfering the floor impact noise to eliminate the noise. The noise not having been suppressed is detected by an error sensor and processed together with the noise detected by the reference sensor by the control unit, thus a sound wave to be emitted from the speaker is corrected appropriately.

Abstract: An active noise cancellation system (26) for controlling engine noise propagation through a vehicle induction system (32) is customizable to achieve a desired engine noise profile. A controller (34) of the active noise cancellation system drives a speaker (36) to generate a noise cancellation sound in a manner consistent with an individual's indicated preference for a specific type of available engine noise profile. By customizing how the speaker is driven, the system customizes the resulting engine noise heard in the passenger compartment. In one example, the system is customizable using a hand held communication device (24) such as a cell phone, a personal digital assistant or a so-called palm top computer. In another example, a resident communication bus on the vehicle is accessed through a user communication interface (28) supported on the vehicle.

Abstract: A method and apparatus for actively influencing the intake noise of an internal combustion engine. The apparatus comprises a controller (7) which senses the actual noise (I) via a microphone (16) and compares the actual noise with a reference noise signal which depends on the engine speed D and at least one further engine parameter P, such as, for example, the throttle (12) position. A comparison signal V generated by comparing the actual noise to the reference noise value is used to adjust a control signal Asum, which also depends on the engine speed D. The control signal is fed to an electromechanical transducer (14) which generates a correcting noise (20) which is superimposed on the intake noise (21) to produce the resultant actual noise (22), which should correspond as closely as possible to the reference noise value.

Abstract: A selective noise canceling device is disclosed that evaluates an external audio signal and determines whether a given external audio signal should be suppressed or reproduced. A selective noise suppression circuit processes the external audio signal to classify the external audio signal as noise to be suppressed or as a desired audio signal to be reproduced. An external audio signal, or a desired portion thereof, is reproduced if a portion of the external audio signal is likely to be of interest to the user. The desired external signal may optionally be amplified over the primary selected audio signal for emphasis and the selected audio signal may optionally be suppressed entirely when the desired external signal is reproduced.

Abstract: A process for determining an estimated value for the noise level n of a background noise superimposed on an acoustic useful signal is characterised in that the estimated value n(x) for a sampled input signal x(k) is defined as a value n1(x) which is determined by means of the minimum value of the quantity of all the successive maximum values of the input signal x(k) in each case found within a short time interval ts≧1 ms; that the value n1(x) is adopted as estimated value n(x) for the current noise level n when the dynamic variations of the input signal x(k) undershoot a threshold value &egr;; and that otherwise the estimated value determined in the preceding step is adopted unchanged as new estimated value n(x). In this way it is possible to achieve an extremely exact determination of the current noise level with very fast adaptation times which are considerably shorter than in known processes, with the need for only a relatively small computation outlay.

Abstract: An active noise controller includes a duct (2) of a stainless steel having the shape of a pipe and provided with an opening (1) at a first end thereof, and a loudspeaker (3)connected to a second end of the duct (2). The duct (2) is disposed with its opening (1) located at a distance not greater than half the wavelength of a sound produced by a sound source (4) from the sound source (4) so as to face the sound source (4). A sound produced by the vibration of the vibrating member (5) of the loudspeaker (3) travels from the second end of the duct (2) through the duct (2) to the first end of the same, and the sound is radiated toward the sound source (4). The sound radiated through the opening (1) has a frequency substantially equal to that of an unnecessary sound included in the sound produced by the sound source (4), an amplitude substantially equal to that of the unnecessary sound and a phase substantially opposite to that of the unnecessary sound.

Abstract: An active noise cancellation aircraft headset system. A speaker is mounted within each earcup of a headset for receiving and acoustically transducing a composite noise cancellation signal. A microphone is also mounted within each earcup for transducing acoustic pressure within the earcup to a corresponding analog error signal. An analog filter receives the analog error signal and inverts it to generate an analog broadband noise cancellation signal. The analog error signal is also provided to an analog to digital converter, which receives the analog microphone error signal and converts it to a digital error signal. A DSP takes the digital error signal and, using an adaptive digital feedback filter, generates a digital tonal noise cancellation signal. A digital to analog converter then converts the digital tonal noise cancellation signal to an analog tonal noise cancellation signal so that it can be combined with the analog broadband noise cancellation signal.

Abstract: A fan noise canceller comprises a rotation information detecting means 2 (or 12) for detecting noise information of a fan 1 (11), a band-pass filter 3 (13) for extracting the blade passing frequency from the noise information, an output control means 4 (14) for controlling the amplitude and phase of the blade passing frequency signal of the extracted noise information, and a cancelling loud-speaker 2 (25) for converting the output of the output control means 4 (41) into a sound signal. The rotation information detecting mean 2 (21) Yincludes a rotatable disc 2A coupled to the shaft of the fan 1 (11) and carrying change information corresponding to the number of fan blades, and a photo-interrupter 2B for outputting signals of the blade passing frequency and harmonics thereof contained in the rotation information of the rotatable disc 2A as electric signals.