439 results about "Noise spectrum" patented technology

Scalable coding of audio into a core layer in response to a desired noise spectrum established according to psychoacoustic principles supports coding augmentation data into augmentation layers in response to various criteria including offset of such desired noise spectrum. Compatible decoding provides a plurality of decoded resolutions from a single signal. Coding is preferably performed on subband signals generated according to spectral transform, quadrature mirror filtering, or other conventional processing of audio input. A scalable data structure for audio transmission includes core and augmentation layers, the former for carrying a first coding of an audio signal that places post decode noise beneath a desired noise spectrum, the later for carrying offset data regarding the desired noise spectrum and data about coding of the audio signal that places post decode noise beneath the desired noise spectrum shifted by the offset data.

A single stage, single switch, input-output isolated converter configuration which uses a hybrid combination of forward and flyback converters is disclosed. The converter operates at a high input power factor with a regulated DC output voltage. It makes use of a novel control scheme utilizing duty cycle control at two discrete operating frequencies. Although the invention employs two frequencies, it does not use a continuous frequency variation. This configuration has the advantage of reduced peak current stresses on the components and is specifically suited for ‘buck’ applications where low DC output voltages (e.g. 24V, 48V) are needed. This configuration will be of specific interest to industries associated with battery charging and uninterruptible power supply (UPS) systems. Apart from having several competitive features compared with prior art techniques, the dual frequency operation scheme reduces the amplitude of its noise spectrum by spreading it over a wider frequency range thus making it more electromagnetic compatible.

Road noise is reduced without locally storing noise spectrum patterns for determination or without detecting the present position of a vehicle from the device. An in-vehicle hands-free device causes a cellular phone to detect the present position of the vehicle and transmit the position to a server. The server determines a noise spectrum pattern corresponding to the road surface on which the vehicle is presently running. The noise spectrum pattern is based on the present position of the vehicle received from the in-vehicle hands-free device and road information. The server transmits the noise spectrum pattern to the in-vehicle hands-free device whereupon a noise canceling signal is superimposed on a received signal. The noise canceling signal is based on an inverted noise spectrum pattern that is obtained by inverting the phase of the noise spectrum pattern. The resulting composite signal is output from a speaker.

A communication device includes a noise flattening filter having a filter response that dynamically adjusts based on the current noise spectrum in a wireless channel. The noise spectrum of the wireless channel is estimated and used to determine a noise classification for the channel. A noise flattening filter response is then selected based upon the noise classification for use in filtering signals received from the channel. The filtered signals are then delivered to an equalizer for further processing.

A noise suppression apparatus of the present invention includes a voice/non-voice discriminator for discriminating a frame signal divided into frames having a predetermined length; a Fourier transform unit for converting a frame signal into a spectrum; a noise spectrum estimation unit for estimating a noise spectrum of a frame judged as a non-voice signal; an amplitude spectrum subtractor for subtracting the product of an estimated noise spectrum and a predetermined coefficient from a spectrum obtained by the transform unit; an auditory correction noise adder for adding aa auditory correction noise spectrum to a spectrum outputted from the subtractor; and an inverse Fourier transform unit for performing inverse Fourier transform to an output of the adder. The noise suppression apparatus further includes a negative amplitude value counter for counting the number of frequency components in an output of the subtractor whose amplitude values are negative; a subtraction coefficient setting unit for gradually decreasing a subtraction coefficient unit the counted value becomes not more than a predetermined value; an inverse Fourier transform unit for performing inverse Fourier transform to an output of the counter; and a noise spectrum estimation unit for calculating spectrum information of noise in the frame signal using different spectrum information according to the current type of frame signal.

A system and method for receiving telemetry data from implantable medical devices such as cardiac pacemakers with improved noise immunity is disclosed. Ambient noise levels and signal strength are monitored and used to adaptively adjust the detection sensitivity of the receiver. Filtering of the received signal is performed to remove both broadband and narrowband noise. Removal of narrowband noise is accomplished with notch filters that are dynamically adjusted in accordance with a detected noise spectrum.

Methods and apparatus for maximizing speech intelligibility use psycho-acoustic variables of a model of speech perception to control the determination of optimal frequency-band specific gain adjustments. Speech signals (or other audio input) whose intelligibility is to be improved are characterized by parameters which are applied to the model. These include measurements or estimates of speech intensity level, average noise spectrum of the incoming audio signal, and/or the current frequency-gain characteristic of the hearing compensation device. Characterizations of listeners based on hearing test results, for example, may also be applied to the model. Frequency-band specific gain adjustments generated by use of the model can be used for hearing aids, assistive listening devices, telephones, cellular telephones, or other speech delivery systems, personal music delivery systems, public-address systems, sound systems, speech generating systems, or other devices or mediums which project, transfer or assist in the detection or recognition of speech.

A signalling method for controlling unnecessary power increases and call drop during discontinuous transmission (DTX) mode of a frame-based transmission system. The signalling method comprises the steps of (1) detecting, at a receiver end of the transmission system a status of a transmitted frame indicating one of two possible transmission modes including (a) when a gating-off of the traffic channel occurs, and (b) when no gating-off of traffic occurs and normal traffic is being transmitted, and (2) controlling a change in the receiver target bit energy to noise spectrum density ratio Eb/No in response to the detection step so that a receiver target Eb/No is increased only when the detecting step does not indicate a gating-off of traffic has occurred.

A robust watermark embedded into a Direct Stream Digital (DSD) audio signal including a flat frequency response in a specific frequency range which does not extend below 20 kHz or above 100 kHz. The watermark is therefore hidden in the noise spectrum of the DSD signal, such that the watermark is inaudible to a listener. Since the noise spectrum contains important information that helps provide the DSD signals with sharp transients and an accurate impulse response, the watermark cannot be removed from the DSD signal without causing significant degradation to the signal's audio quality.

An error voltage Verr, as amplified by an amplifier, and an input voltage Vin, are multiplied together by a multiplier to generate a first threshold value signal Vth1, which is in phase with and similar in waveform to the input voltage Vin, and proportional in amplitude to the error voltage Verr. A second threshold value signal Vth2 is generated from the first threshold value signal Vth1 by a series circuit of a diode and a resistor. The power factor is increased by on/off-control of a switching element via a drive circuit, so that a current detection signal Vi, which is detected by a resistor and corresponds to an input current, falls between the two threshold value signals Vth1 and Vth2. Since the off time is not fixed, the noise spectrum is spread and increase of the switching frequency is suppressed. Noise reduction thus can be attained.

Speech/non-speech determining section 103 makes a speech/non-speech determination of whether a speech spectrum is of a speech interval with a speech included or of a non-speech interval with only a noise and no speech included. Noise spectrum estimating section 104 estimates a noise spectrum based on the speech spectrum determined as the non-speech interval. SNR estimating section 105 obtains speech signal power from the speech interval and noise signal power from the non-speech interval in the speech spectrum, and calculates SNR from a ratio of two values. Based on the speech/non-speech determination and a value of SNR, suppression coefficient control section 106 outputs a suppression lower limit coefficient to spectrum subtraction section 107. Spectral subtraction section 107 subtracts an estimated noise spectrum from the input speech spectrum, and outputs a speech spectrum with a noise suppressed.

The invention relates to a method of estimating noise power spectral density PSD in an input sound signal comprising a noise signal part and a target signal part. The invention further relates to a system to its use. The object of the present invention is to provide a scheme for estimating the noise PSD in an acoustic signal consisting of a target signal contaminated by acoustic noise. The problem is solved by a method comprising the steps of d) providing a digitized electrical input signal to a control path and performing; d1) storing a number of time frames of the input signal each comprising a predefined number N2 of digital time samples x_n (n=1, 2, . . . , N₂), corresponding to a frame length in time of L₂=N₂/f_s; d2) performing a time to frequency transformation of the stored time frames on a frame by frame basis to provide corresponding spectra Y of frequency samples; d3) deriving a periodogram comprising the energy content |Y|² for each frequency sample in a spectrum, the energy content being the energy of the sum of the noise and target signal; d4) applying a gain function G to each frequency sample of a spectrum, thereby estimating the noise energy level |Ŵ|² in each frequency sample, |Ŵ|²=G·|Y|²; d5) dividing the spectra into a number N_sb2 of sub-bands, each sub-band comprising a predetermined number n_sb2 of frequency samples, and assuming that the noise PSD level is constant across a sub-band; d6) providing a first estimate |{circumflex over (N)}|² of the noise PSD level in a sub-band based on the non-zero noise energy levels of the frequency samples in the sub-band; d7) providing a second, improved estimate |Ñ|² of the noise PSD level in a sub-band by applying a bias compensation factor B to the first estimate, |Ñ|²=B·|{circumflex over (N)}|². The invention may e.g. be used in listening devices, e.g. hearing aids, mobile telephones, headsets, active earplugs, etc.

The invention provides a water supply pipeline leakage detecting and positioning method which is characterized in that a signal collected by a sensor is subjected to enhancement through spectral subtraction, the frequency spectrum variance of the signal after enhancement is calculated, a double-threshold method is adopted for judgment, that is, if the frequency spectrum variance is within the threshold range, which indicates that leakage occurs, the leakage point is positioned, a BP neural network is utilized to form a filter, a water leakage signal is separated from noise and subjected to generalized correlation analysis, time delay estimation is carried out according to the weight function with a good signal-to-noise ratio selectivity, three time delays of the sensor are acquired, and a water leakage positioning model is utilized for calculation to acquire water leakage point position information. According to the water supply pipeline leakage detecting and positioning method, the spectral subtraction method is adopted for signal enhancement, the double-threshold method is utilized for leakage judgment, if the frequency spectrum variance is within the threshold range, which indicates that leakage occurs, and therefore the accuracy is higher; besides, the non-leakage estimation method is adopted for estimation of the noise spectrum, the signal-to-noise ratio is increased more obviously, meanwhile the BP neural network is adopted for filtering, the generalized correlation time delay estimation accuracy is improved, and the water leakage point positioning accuracy is effectively improved.

A semiconductor device simulation method includes the step of storing, in a storage unit, a surface potential and threshold voltage obtained by computation, the step of computing thermal drain noise on the basis of the data of the surface potential and thermal drain noise stored in the storage unit, and the step of determining whether or not to reduce thermal drain noise, and reflecting the computation result in simulation of the model when it is determined that thermal drain noise is to be reduced. A drain current I_ds of a MOSFET is calculated and substituted into a relational expression for a drain current noise spectrum density obtained from a Nyquist theorem equation, thereby calculating a thermal drain noise coefficient γ of the MOSFET by substituting the current I_ds into a relational expression for a thermal drain noise spectrum density which is obtained from the Nyquist logical equation.

A spectrum calculating unit calculates, for each of the frames, a spectrum by performing a frequency analysis on an acoustic signal. An estimating unit estimates a noise spectrum. An energy calculating unit calculates an energy characteristic amount. An entropy calculating unit calculates a normalized spectral entropy value. A generating unit generates a characteristic vector based on the energy characteristic amounts and the normalized spectral entropy values that have been calculated for a plurality of frames. A likelihood calculating unit calculates a speech likelihood value of a target frame that corresponds to the characteristic vector. In a case where the speech likelihood value is larger than a threshold value, a judging unit judges that the target frame is a speech frame.

A non-vented shell earplug for insertion into the ear canal has multiple chambers configured as coupled acoustic resonators. Each chamber is provided with an acoustic element having inertia and resistance coupling the chamber to its neighbor to form multiple resonant chambers. The dimensions of the individual acoustic elements set the frequency response of the earplug, and determine the attenuation characteristics of the resonators. Unlike the single chamber resonator of the prior art, the multiple-resonator earplug provides attenuation in both low and high frequency segments of the noise spectrum.

Additionally, the present invention teaches placing loudspeaker and/or sound sensing transducer for sound communication purposes and active noise control within the earplug, with their sound field patterns directed into a chamber for coupling to the ear canal. The use of multiple resonators enhances the high frequency communications response of the earplug.

The invention discloses a noised voice end point robustness detection method. The method comprises the following steps of constructing an estimation method of a noise power spectrum of each frame of acoustical signals in filtering and providing a time-varying updating mechanism of a noise spectrum; firstly, carrying out iterative wiener filtering on a frequency spectrum of each frame of voices; then, dividing into several sub-band and calculating a frequency spectrum entropy of each sub-band; and then making successive several frames of sub-band frequency spectrum entropies pass through one group of median filters so as to acquire each frame of the frequency spectrum entropies; according to values of the frequency spectrum entropies, classifying input voices. By using the algorithm, the voices and noises, and a voice state and a voiceless state can be effectively distinguished. Under different noise environment conditions, robustness is possessed. The algorithm has low calculating cost, is simple, is easy to realize and is suitable for application of real-time voice signal processing system of various kinds of systems needing voice end point detection. The method is a real-time voice end points detection algorithm which adapts to a complex environment, and voice end point detection and voice filtering enhancement are completed together in a one-time state.

A system and method for generating a masking noise level and spectrum automatically adjusted to obtain a target masking noise spectrum in a room. The system comprises a white noise generator and a mask filter automatically determined according to a correction of an acoustical response of the room and to the target masking noise corrected by an ambient noise.

In a power converter having m=two or more channels of power factor correction (PFC) circuits connected in parallel and an electromagnetic interference (EMI) filter connected in series therewith, phase shifts in switching between the respective PFC channels can allow increase of EMI filter corner frequency allowing reduction of size and cost of the EMI filter at some switching frequencies. Asymmetrical phase shifts (other than 360°/m) such as 360°/2m and other phase shifts and variations in m allow increase of EMI filter corner frequency at switching frequencies where symmetrical, 360°/m phase shifts provide no benefit to EMI filter design by providing cancellation or partial cancellation of different harmonics of the switching noise; which cancellation may be arranged to be complementary to the EMI filter function at more than one peak of the noise spectrum. (Such asymmetrical phase shifts do not significantly increase ripple and consequent switching noise). Alteration of m and corresponding alteration of phase shift may be performed adaptively for purposes of improving efficiency at light loads and the like.

An error voltage Verr, being a difference between DC output voltage Vout and output reference voltage Vref, and an input voltage Vin are multiplied to produce first threshold voltage signal Vth1 in phase with and similar to input voltage Vin and proportional to Verr. Second threshold voltage signal Vth2 is produced from first threshold voltage signal Vth1. The input current is detected as a current detection signal Vi across a resistor 12, whether it is between the threshold value signals is detected by a current range detecting circuit, and accordingly, the timing of turning on or off switching device is controlled so that at least one of an duration on and an off duration of the switching device is limited to enhance a power factor. Unfixed off duration disperses a noise spectrum to prevent an increase in switching frequency, to reduce noise.