Abstract: The active noise control device includes: a signal obtaining section that obtains an electric signal relating to the predetermined sound; a control section that adjusts an amplitude and a phase of the electric signal obtained by the signal obtaining section; a vibrating section having a diaphragm and a vibrator, the vibrator vibrating in accordance with an output from the control section. Because a sound radiated from the diaphragm toward the first region is substantially in opposite phase to that toward the second region, the control section controls the vibrator so that the diaphragm generates a sound that attenuates the predetermined sound in the first region, and causes the predetermined sound to have a desired frequency characteristic in the second region.

Abstract: A noise cancellation signal is generated by generating an ambient noise signal, representing ambient noise, and generating a noise cancellation signal, by applying the ambient noise signal to an feedforward filter, where the feedforward filter comprises a high-pass filter having an adjustable cut-off frequency, and by applying a controllable gain. The noise cancellation signal is then applied to a loudspeaker, to generate a sound to at least partially cancel the ambient noise. An error signal is generated, representing unwanted sound in the region of the loudspeaker. The phase of the ambient noise signal is compared to a phase of the error signal, and the gain is controlled on the basis of a result of the comparison, taking account of a phase shift introduced by the high-pass filter when performing the comparison.

Abstract: In an aspect, the invention features an active noise reduction device including an electronic signal processing circuit. The electronic signal processing circuit includes a first input for accepting a first signal, a second input for accepting a second signal, an output for providing a third signal, a feed-forward path from the first input to the output, and a feed-forward controller for determining the control parameter by calculating a control signal using the first signal and the second signal and then using the control signal to determine the control parameter. The feed-forward path includes a fixed compensation linear filter and a variable compensation filter having an input for receiving a control parameter that applies a selected linear filter from a family of linear filters that vary in both gain and spectral shape and are selectable by the control parameter.

Abstract: A method of signal processing an input signal in a hearing aid to avoid entrainment, the hearing aid including a receiver and a microphone, the method comprising using an adaptive filter to measure an acoustic feedback path from the receiver to the microphone and adjusting an adaptation rate of the adaptive filter using an output from a filter having an autoregressive portion, the output derived at least in part from a ratio of a predictive estimate of the input signal to a difference of the predictive estimate and the input signal.

Abstract: An active noise reduction earphone. The earphone includes structure for positioning and retaining the earphone in the ear of a user without a headband, active noise reduction circuitry including an acoustic driver with a nominal diameter greater than 10 mm oriented so that a line parallel to, or coincident with, an axis of the acoustic driver and that intersects a centerline of the nozzle intersects the centerline of the nozzle at angle ?>±30 degrees. A microphone is positioned adjacent an edge of the acoustic driver. The earphone is configured so that a portion of the acoustic driver is within the concha of a user and another portion of the acoustic driver is outside the concha of the user when the earphone is in position. An opening coupling the nozzle to the environment includes impedance providing structure in the opening.

Abstract: Microphone arrays (MAs) are described that position and vent microphones so that performance of a noise suppression system coupled to the microphone array is enhanced. The MA includes at least two physical microphones to receive acoustic signals. The physical microphones make use of a common rear vent (actual or virtual) that samples a common pressure source. The MA includes a physical directional microphone configuration and a virtual directional microphone configuration. By making the input to the rear vents of the microphones (actual or virtual) as similar as possible, the real-world filter to be modeled becomes much simpler to model using an adaptive filter.

Abstract: Systems and methods of improved noise reduction include the steps of: receiving an audio signal from two or more acoustic sensors; applying a beamformer to employ a first noise cancellation algorithm; applying a noise reduction post-filter module to the audio signal including: estimating a current noise spectrum of the received audio signal after the application of the first noise cancellation algorithm, wherein the current noise spectrum is estimated using the audio signal received by the second acoustic sensor; determining a punished noise spectrum using the time-average level difference between the audio signal received by the first acoustic sensor and the current noise spectrum; determining a final noise estimate by subtracting the punished noise spectrum from the current noise spectrum; and applying a second noise reduction algorithm to the audio signal received by the first acoustic sensor using the final noise estimate; and outputting an audio stream with reduced background noise.

Abstract: An Active Noise Control (ANC) for controlling a noise produced by a noise source may include an acoustic sensor (212) to sense a noise pattern and to produce a noise signal corresponding to the sensed noise pattern, an estimator (202) to produce a predicted noise signal by applying an estimation function to the noise signal, and an acoustic transducer (216) to produce a noise destructive pattern based on the predicted noise signal.

Abstract: Robust feedforward active noise cancellation is provided which can overcome or substantially alleviate problems associated with the diverse and dynamic nature of the surrounding acoustic environment. A multi-faceted analysis is performed to determine the direction (or directions) of propagation of noise in the surrounding acoustic environment. The direction of propagation is then utilized to determine direction-dependent characteristics of the acoustic path between a reference position where the noise is captured and a desired position where the noise is to be cancelled. These characteristics are used to form a feedforward signal adapted to cancel the noise at the desired position. By forming the feedforward signal based on direction-dependent characteristics of the acoustic path, the techniques described herein can achieve optimal noise cancellation at the desired location, regardless of the direction of propagation of the noise.

Abstract: An apparatus includes a member configured to form an acoustic seal around a portion of an acoustic environment, and active noise reduction circuitry. The active noise reduction circuitry includes: detection circuitry configured to detect a change in pressure within the acoustic environment caused by movement of the member, and gain compensation circuitry configured to change a loop gain of a feedback loop in response to the detected change in pressure.

Abstract: VoIP phones according to the present invention include a microphone, which may be internal or external, and allow the user to communicate unobtrusively, check voice mail and conduct other activities in an environment which can be noisy in general and extremely noisy sometimes. Speech recognition functionally may also be used to generate and send touch tone or DTMF tones such as in response to call trees or voice recognition functionality used by airlines, credit card companies, voice mail systems, and other applications. A system and method of audio processing which provides enhanced speech recognition is provided. Audio input is received at the microphone which is processed by adaptive noise cancellation to generate an enhanced audio signal. The operation of the speech recognition engine and the adaptive noise canceller may be advantageously controlled based on Voice Activity Detection (VAD).

Abstract: According to one embodiment, a sound signal compensation apparatus includes an input module, a compensation module, and an output module. The input module receives identification information identifying a first frequency with regard to a resonance of an ear closed by an earphone or headphone. The compensation module performs first compensation emphasizing a second frequency on a sound signal, the second frequency being determined based on the identification information or the first frequency. The output module outputs the compensated sound signal. The compensation module is configured to perform the first compensation emphasizing the second frequency, at which emphasis is greater than or equal to 2 dB and less than or equal to 12 dB.

Abstract: An encoding apparatus comprises a frame processor (105) which receives a multi channel audio signal comprising at least a first audio signal from a first microphone (101) and a second audio signal from a second microphone (103). An ITD processor 107 then determines an inter time difference between the first audio signal and the second audio signal and a set of delays (109, 111) generates a compensated multi channel audio signal from the multi channel audio signal by delaying at least one of the first and second audio signals in response to the inter time difference signal. A combiner (113) then generates a mono signal by combining channels of the compensated multi channel audio signal and a mono signal encoder (115) encodes the mono signal. The inter time difference may specifically be determined by an algorithm based on determining cross correlations between the first and second audio signals.

Abstract: An adaptive control unit is described for receiving an analog input signal containing at least an indication of a parameter to be controlled to generate an analog output signal for control of the parameter. The analog input signal contains a fed back component resulting from the analog output signal. The adaptive control unit comprises an analog filter having an adjustable gain, a gain adjuster for adjusting the gain of the analog filter using a feedforward adjustment method, and a filter for compensating for the fed back component in the analog input signal.

Abstract: An active noise cancellation system that reduces, at a listening position, power of a noise signal radiated from a noise source to the listening position. The system includes an adaptive filter, at least one acoustic actuator and a signal processing device. The adaptive filter receives a reference signal representing the noise signal, and provides a compensation signal. The at least one acoustic actuator radiates the compensation signal to the listening position. The signal processing device evaluates and assesses the stability of the adaptive filter.

Abstract: In an aspect, in general, a feedback based active noise reduction system is configured to detect actual or potential instability by detecting characteristics of the system related to potential or actual unstable behavior (e.g., oscillation) and adapt system characteristics to mitigate such instability.

Abstract: The invention relates to a noise canceling audio transmitting/receiving device; a stereo headset with an integrated array of microphones utilizing an adaptive beam forming algorithm. The invention also relates to a method of using an adaptive beam forming algorithm that may be incorporated into a stereo headset. The sensor array used herein has adaptive filtering capabilities.

Abstract: A noise reduction device of the present invention comprises a control filter unit for generating a control sound signal to cancel out a noise, a control speaker for outputting a control sound according to the control sound signal from the control filter unit, an error microphone for detecting a residual sound by superimposing the noise upon the control sound output from the control speaker, and an obstacle detector for detecting an obstacle around the error microphone, wherein the control filter unit generates the control sound signal according to data from the error microphone and the obstacle detector.

Abstract: A noise reduction device is disclosed, in which noise reduction device, a controlling sound generator outputs a white noise generated by a white-noise generator, and this white noise is sensed by an error sensor for identifying an acoustic transmission function covering a path from the controlling sound generator to the error sensor. At this time, an identification controller prompts the white noise generator to generate a white noise for identifying the acoustic transmission function provided that an ambient noise level sensed by the error sensor is not greater than a given threshold.

Abstract: An active noise cancellation fault detector (NCFD) is presented that is configured to cancel normal machine noise in an operator cabin, while allowing noise associated with a machine failure mode to remain so that an operator can hear when a machine component is beginning to fail or is in a failure mode. An NCFD can generate a model waveform of normal noise scaled to machine operating parameters. The model waveform can be inverted and adjusted in gain and phase to provide a cancellation waveform. The invention can be configured to determine operator location within a machine cab so that cancellation signals can be configured with the proper phases to destructively interfere with normal machine noise within a quiet zone or noise suppression envelope around an operator. Noise within the quiet zone can be detected and compared to various fault waveforms to determine whether a machine component is beginning to fail.

Abstract: Systems and methods to reduce the negative impact of wind on an electronic system include use of a first detector that receives a first signal and a second detector that receives a second signal. A voice activity detector (VAD) coupled to the first detector generates a VAD signal when the first signal corresponds to voiced speech. A wind detector coupled to the second detector correlates signals received at the second detector and derives from the correlation wind metrics that characterize wind noise that is acoustic disturbance corresponding to at least one of air flow and air pressure in the second detector. The wind detector controls a configuration of the second detector according to the wind metrics. The wind detector uses the wind metrics to dynamically control mixing of the first signal and the second signal to generate an output signal for transmission.

Abstract: Various embodiments reduce noise within a particular environment, while isolating and capturing speech in a manner that allows operation within an otherwise noisy environment. In one embodiment, an array of one or more microphones is used to selectively eliminate noise emanating from known, generally fixed locations, and pass signals from a pre-specified region or regions with reduced distortion.

Abstract: Systems and methods to reduce the negative impact of wind on an electronic system include use of a first detector that receives a first signal and a second detector that receives a second signal. A voice activity detector (VAD) coupled to the first detector generates a VAD signal when the first signal corresponds to voiced speech. A wind detector coupled to the second detector correlates signals received at the second detector and derives from the correlation wind metrics that characterize wind noise that is acoustic disturbance corresponding to at least one of air flow and air pressure in the second detector. The wind detector controls a configuration of the second detector according to the wind metrics. The wind detector uses the wind metrics to dynamically control mixing of the first signal and the second signal to generate an output signal for transmission.

Abstract: The present technology provides systems and methods for robust feedforward active noise cancellation which can overcome or substantially alleviate problems associated with the diverse and dynamic nature of the surrounding acoustic environment. A multi-faceted analysis decouples the background noise within the earpiece from the acoustic wave (e.g. the anti-noise and desired audio) generated by an audio transducer within the earpiece. A difference signal is formed utilizing monitoring signals captured by array of monitoring microphones within the earpiece. The difference signal is formed such that contributions due to the acoustic wave generated by the audio transducer are selectively attenuated. As a result, the difference signal indicates an acoustic energy level of the background noise within the earpiece.

Abstract: In one aspect, in general, an active noise reduction system detects actual or potential instability by detecting characteristics of the system related to potential or actual unstable behavior (e.g., oscillation) and adapts system characteristics to mitigate such instability. In some examples, the system adapts to variation in characteristics of an acoustic component of a feedback path that has or may induce unstable behavior to improve a user's acoustic experience.

Abstract: A noise control device eliminates a possibility that a noise arriving at a control point is increased as compared to a case where noise control is not performed and has a reduced circuit scale. The device includes a controlling noise detector for detecting a given noise to output a controlling noise signal, a controlling filter section for signal-processing the controlling noise signal, by using a preset fixed filter coefficient, to output a control signal, and a control speaker for reducing the given noise, by emitting toward the control point a control sound based on the control signal. The device also includes a noise determination section for determining whether the given noise is a noise corresponding to the fixed filter coefficient, and an output control section for stopping output of the control signal from the controlling filter section when the given noise does not correspond.

Abstract: The subject matter of this specification can be embodied in, among other things, a computer-implemented method for removing noise from audio that includes building a sound model that represents noises which result from activations of input controls of a computer device. The method further includes receiving an audio signal produced from a microphone substantially near the computer device. The method further includes identifying, without using the microphone, an activation of at least one input control from among the input controls. The method further includes associating a portion of the audio signal as corresponding to the identified activation. The method further includes applying, from the audio model, a representation of a noise for the identified activation to the associated portion of the audio signal so as to cancel at least part of the noise from the audio signal.

Abstract: A method and a system for the active reduction, at a predetermined area, of the energy of a sound signal (dk(n)), also called a diffused noise signal, generated at the area by a primary signal (xk(n)), or noise signal, by the emission of a plurality of counter-noise signals (yk(n)) having an effect antagonistic to the diffused noise signal (dk(n)), each of the counter-noise signals (yk(n)) including a feedback counter-noise signal (yfbkk(n)) and a feed-forward counter-noise signal (yfwdk(n)). The method includes detecting the periodical components of diffused noise signal (dk(n)) for adjusting the feedback counter-noise signal (yfbkk(n)), and modelling the inverse of the secondary path for adjusting the feedback counter-noise (yfbkk(n)) and feed-forward counter-noise (yfwdk(n)) signals. The invention can be implemented to any type of industrial or non-industrial noise and in any location such as working places and relaxation places.

Abstract: A noise canceling and communication system includes an in-ear device adapted to fit in the ear canal of a device user. A passive noise reduction element reduces external noise entering the ear canal. An external microphone senses an external acoustic signal outside the ear canal. An internal microphone senses an internal acoustic signal proximal to the tympanic membrane. One or more internal sound generators produce a noise cancellation signal and an acoustic communication signal, both directed towards the tympanic membrane. A probe tube shapes an acoustic response between the internal sound generator and the internal microphone to be relatively constant over a wide audio frequency band. An electronics module is located externally of the ear canal and in communication with the in-ear device for processing the microphone signals using a hybrid feed forward and feedback active noise reduction algorithm to produce the noise cancellation signal.

Abstract: Disclosed herein is a noise canceling apparatus including: a microphone configured to pick up ambient sound as noise; a first signal generator configured to receive a signal from the microphone to generate a noise cancel signal that is inverted in phase to the signal received from the microphone and has an amplitude level considered with an attenuation in accordance with a distance from the microphone to an observation point separated away from the microphone; a first loudspeaker configured to be arranged in the proximity of the microphone and output the noise cancel signal; a second signal generator configured to receive the signal from the microphone to generate a positive-phase signal that has the same phase as that of the signal from the microphone; and a second loudspeaker configured to be arranged in the proximity of the microphone and output the positive-phase signal.

Abstract: A method for measuring performance of a noise cancellation system that is operable to cancel noise is provided. The method includes generating a first model of a target noise. The first model represents the target noise in a form that is received at a location remote from a noise source of the target noise and within a defined environment. The method also includes generating a second model of a cancellation noise. The cancellation noise is configured to at least partially cancel the target noise when combined with the target noise. The second model represents the cancellation noise in a form that is received at the location. The method also includes determining, using the first model and the second model, a cancellation error value indicative of only a portion of the target noise that remains when the target noise and the cancellation noise are combined.

Abstract: Disclosed are an apparatus and a method for transmitting human sound that cancel an interference signal generated by a non-linear property of a human body around an ear by synthesizing and transmitting a sound signal modulated by a single side band (SSB) transmission method and a carrier to one output unit and by synthesizing and transmitting the sound signal modulated by the single side band (SSB) transmission method and a carrier in which a phase of a signal is transited to the other output unit, by using two signal output units in a sound transmitting apparatus.

Abstract: A method for controlling noise of a rotating device includes: obtaining a sound wave signal of noise generated by the rotating device, where the sound wave signal is fed back by a reference sensor; obtaining rotational speed information of the rotating device; and searching a predefined function mapping table according to the rotational speed information to obtain transfer functions; generating a sound emitting command according to the transfer functions and the sound wave signal; and sending the sound emitting command to a secondary source emitting device, so that the secondary source emitting device emits a secondary sound wave, where the secondary sound wave is used to suppress the noise generated by the rotating device.

Abstract: A noise enhancement system for an automobile utilizes a single input of engine speed to derive a control signal used to drive a speaker. The speaker generates sounds that enhance or replicate the desired sounds from the engine. The output from the speaker is crafted dependent on the vehicle operating conditions. Instead of multiple transducers and inputs the noise enhancement system of this invention utilizes the single input of engine RPM engine speed. By utilizing only engine speed, the noise enhancement system is cost effective and significantly less complex.

Abstract: Provided are an apparatus and method for preventing noise. The apparatus estimates a noise signal from a signal transformed into a frequency domain, uses the estimated noise signal to estimate the amplitude of the frequency-domain signal according to a frequency band, and then calculates a phase difference according to a frequency band and eliminates or prevents noise from the amplitude-estimated frequency-domain signal based on the calculated phase difference according frequency band.

Abstract: A noise reduction device include at east a cavity; a plurality of ducts noise reduction, at least one of the ducts being connected to the cavity for transmitting an acoustic signal including a noise signal into/out of the cavity; a noise reduction circuit, for receiving the acoustic signal including the noise signal and generating an electrical signal; a microphone for receiving the acoustic signal inside the cavity, converting the received acoustic signal into another electrical signal and transmitting the electrical signal to the noise reduction circuit; and a speaker for receiving the electrical signal generated by the noise reduction circuit, using the received electrical signal to generate an out of phase acoustic signal accordingly, and feeding the out of phase acoustic signal into the cavity to interfere with the noise signal inside the cavity. With the noise reduction circuit and cavity structure designed in the noise reduction device, the full range of noise is attenuated.

Abstract: The present invention provides a method and apparatus for finding an estimate of the delay of a signal travelling between two points. A quantity is evaluated from the signal at a final number of time instants, at both a reference point and a reception point. The values are quantized by comparison with a threshold adapted to a typical magnitude of the quantity. If the quantized values from the reception point are shifted back by the true delay with respect to the quantized values from the referenced point, then certain co-occurrences of quantized values have very low probability. Hence, the best delay estimate is that shift which yields the least number of low-probability co-occurrences.

Abstract: In an aspect, the invention features an active noise reduction device including an electronic signal processing circuit. The electronic signal processing circuit includes a first input for accepting a first signal, a second input for accepting a second signal, an output for providing a third signal, a feed-forward path from the first input to the output, and a feed-forward controller for determining the control parameter by calculating a control signal using the first signal and the second signal and then using the control signal to determine the control parameter. The feed-forward path includes a fixed compensation linear filter and a variable compensation filter having an input for receiving a control parameter that applies a selected linear filter from a family of linear filters that vary in both gain and spectral shape and are selectable by the control parameter.

Abstract: A method and system for active noise cancellation is provided. The system employs subband processing, and preferably implements over-sampled filterbank. The system is applicable to adaptive noise cancellation, adaptive echo cancellation for portable listening devices, such as headsets and other similar listening devices.

Abstract: Broadly speaking, the embodiments disclosed herein describe an apparatus, system, and method for managing the effects of TDMA noise emitted by a communication device on an audible circuit.

Abstract: A sound reproducing device is provided including a communication unit that transmits/receives signals; at least one sound output unit that outputs sound based upon a signal having been received, a sound pickup unit that picks up sound and generates audio data, an echo canceller unit that stores any echo signal contained in the signal having been received at the communication unit and generates a dummy echo signal by using the stored echo signal, and a noise reducing unit that generates a cancel signal to be used to cancel noise by using the audio data if the sound picked up at the sound pickup unit contains noise originating from a noise source and outputs a composite signal generated by combining the output signal from the echo canceller unit and the cancel signal.

Abstract: The subject matter of this specification can be embodied in, among other things, a computer-implemented method for removing noise from audio that includes building a sound model that represents noises which result from activations of input controls of a computer device. The method further includes receiving an audio signal produced from a microphone substantially near the computer device. The method further includes identifying, without using the microphone, an activation of at least one input control from among the input controls. The method further includes associating a portion of the audio signal as corresponding to the identified activation. The method further includes applying, from the audio model, a representation of a noise for the identified activation to the associated portion of the audio signal so as to cancel at least part of the noise from the audio signal.

Abstract: Microphone arrays (MAs) are described that position and vent microphones so that performance of a noise suppression system coupled to the microphone array is enhanced. The MA includes at least two physical microphones to receive acoustic signals. The physical microphones make use of a common rear vent (actual or virtual) that samples a common pressure source. The MA includes a physical directional microphone configuration and a virtual directional microphone configuration. By making the input to the rear vents of the microphones (actual or virtual) as similar as possible, the real-world filter to be modeled becomes much simpler to model using an adaptive filter.

Abstract: A method of cancelling acoustic echo in a first signal comprising an echo signal of a second signal, comprising: inserting, in an inaudible manner, into the second signal a pseudo-random sequence whose circular autocorrelation comprises a unit impulse and a continuous component; characterizing, in the first signal, by means of the inserted sequence, an acoustic channel followed by the echo signal; estimating the echo signal in the first signal by means of the characterization of the acoustic channel; and cancelling the echo signal by means of the obtained estimation.

Abstract: A noise control device includes a signal processor that detects a noise outputted from a noise source, and generates a control signal based on the noise and a control acoustic system that generates a control sound for canceling the noise, based on the control signal outputted from the signal processor. The noise control device also includes an output correction section that corrects the control signal outputted from the signal processor, in a frequency band for which a noise control process time ?, which is a time period from when the noise is outputted from the noise source to pass through the signal processor and the control acoustic system to when the control sound reaches the control point, is larger than a noise transfer time T, which is a time period from when the noise is outputted from the noise source to when the noise reaches the control point via the noise transfer system (?>T).

Abstract: The invention provides a sound source separation system, a sound source separation method, and an acoustic signal acquisition device which can precisely separate a target sound and a disturbance sound coming from an arbitrary direction, and which ensures miniaturization of a device.

Abstract: A noise reduction system for actively blocking a noise source for a means of transport. The noise reduction system comprises at least one counter sound source and at least one intensity sensor. The at least one counter sound source and the at least one intensity sensor are arranged in a measuring region. In the measuring region, measuring of the noise intensity of the noise source and measuring of the counter sound intensity of the counter sound source are by the intensity sensor. Based on the measured noise intensity and the counter sound intensity, the counter sound source is controllable such that the sound energy input of the noise source can be globally reduced by the counter sound source.

Abstract: An ANR circuit, possibly of a personal ANR device, monitors a sound level of environmental sounds detected by a microphone external to an earpiece in which the ANR circuit is providing feedback-based ANR, and increases or decreases the degree of feedback-based ANR provided in response to the external microphone detecting a higher or lower sound level, respectively. Increasing and decreasing the degree of feedback-based ANR provided may be carried out by changing a variable loop gain of the ANR circuit and/or a range of frequencies of environmental sounds attenuated by the feedback-based ANR.

Abstract: A system and method are provided for smoothing the in-room acoustic magnitude response of an audio reproduction system. An in-room acoustic magnitude response analysis is performed to determine a room resonance induced peak associated with an audio signal. A replica of the audio signal is filtered at the room resonance induced peak. The filtered replica signal is added with the audio signal. Through this, smoothing of the room resonance induced peak may be achieved, such that a subjective impression of transient response and dynamics of the audio signal are preserved.

Abstract: An active silencer includes: a speaker generating control sound which interferes with noise; a microphone detecting noise remaining after the interference as a remaining noise signal; a sound quality evaluation unit evaluating the sound quality of the remaining noise and output a result of the sound quality evaluation; an actuation signal determination unit determining, according to the result of the sound quality evaluation, the detection timing of the frequency component of the remaining noise signal to be used when the control sound is generated for a plurality of bands of the remaining noise, corresponding to the plurality of bands of a reference signal corresponding to the noise; and a control signal generation unit generating and output a control signal for generation of the control sound depending on a plurality of bands of the determined remaining noise signal and a plurality of bands of the reference signal corresponding to the noise.