48 results about "Tonal noise" patented technology

The invention provides a method and apparatus for noise reduction of a signal, for example speech enhancement of a speech signal. The method involves a two-stage algorithm comprising performing a preprocessing first spectral subtraction to remove tonal noise and generate a tonal noise removed signal, and performing a second spectral subtraction to remove noise from the said tonal noise removed signal. In both spectral subtraction stages noise is not removed completely but only to a level below an audible threshold in order to avoid unwanted artifacts.

Disclosed is a hub of an axial fan. The hub includes primary fan blades and splitter blades disposed between pairs of the primary fan blades. The resulting hub has been observed to reduce tonal noise during fan operation.

The system provides a technique for suppressing or eliminating tonal noise in and input signal. The system operates on the input signal at a plurality of frequency bins and uses information generated at a prior bin to assist in calculating values at subsequent bins. The system first identifies peaks in a signal and then determines if the peaks are from tonal effects. This can be done by comparing the estimated background noise of a current bin to the smoothed background noise of the same bin. The smoothed background noise can be calculated using an asymmetric IIR filter. When the ratio of the current background noise estimate to the currently calculated smoothed background noise is far greater than 1, tonal noise is assumed. When tonal noise is found, a number of suppression techniques can be applied to reduce the tonal noise, including gain suppression with fixed floor factor, an adaptive floor factor gain suppression technique, and a random phase technique.

A fan housing is provided with slots formed in the enclosure of the fan housing. The slots are sized appropriately to filter the noise generated during operation of the cooling fan; e.g., tonal noise produced by the rotation of the blades. The slots may either be vented to the outside of the enclosure or closed off.

A processing system generates an output signal which includes desired signal components, and reduces or eliminates tonal noise. The output signal may be provided to any subsequent signal processing system, including voice recognition systems, pitch detectors, and other processing systems. The subsequent processing systems are less likely to mistake tonal input signal noise for desired signal content, to needlessly consume computational resources to analyze noise, and to take spurious actions induced by the tonal noise.

A system is provided for attenuating tonal acoustic noise associated with a single positive displacement compressor, or multiple positive displacement compressors proximately located from each other. A controller selectably controls the rotational speed and the frequency of operation of each of the compressors. The controller controls the rotational speed of the compressors about a predetermined rotational speed, in a random manner, within the pre-selected speed band to reduce the magnitude of the central tonal acoustic frequency of the pressure pulsations and disperse the sound power over a wider acoustic bandwidth.

A turbofan gas turbine engine comprises a fan and an intake duct upstream of the fan. The fan comprises a fan rotor having a plurality of fan blades. The intake duct has a liner, the liner comprising an acoustic liner positioned upstream of the fan and a buzz-saw tone noise liner positioned upstream of the acoustic liner. The buzz-saw tone noise liner is positioned substantially at, or near, an upstream end of the intake duct. The intake duct has a lip and the buzz-saw tone noise liner is positioned at, or near, the lip.

A system and method for regulating pressure inside a vehicle (“cabin pressure”) with reduced noise is disclosed. The system can include a forward gate and an aft gate that can be moved from a closed position to an open position to release cabin pressure in a controlled manner. The forward gate and the aft gate can comprise one or more flow disruptors. A first portion of the flow disruptors can be fixed and a second portion can be moveable between a retracted position and a deployed in position. In the retracted position the one or more flow disruptors can reduce broadband noise through the system by smoothing air flow therethrough. In the second position, the one or more flow disruptors can create boundary layer turbulence. The boundary layer turbulence can prevent, or delay, flow separation reducing tonal noises therethrough. In this manner, flow efficiency can be increased and noise reduced.

An evaporator includes plates disposed in pairs in first and second groups, along spaced tanks. Dimples extend from the interior portions in the first group, and interior fins are disposed against the interior portions of the second group. The dimples enhance the distribution of liquid refrigerant in the passageways and the thermal energy exchange between ambient air and an upstream, low vapor quality flow of fluid passing between upstream and downstream side edges, of the first group of plates. The evaporator also eliminates the tonal noise or whistle under certain transient operating conditions.

A method controlling a wind turbine to avoid tonal noise production is provided. The method comprises acquiring noise data representing noise produced by a wind turbine and acquiring data from a plurality of vibration sensors positioned at different locations about the wind turbine. The method further comprises identifying a region of interest in the noise data, the region of interest being a candidate for containing tonal noise generated by the wind turbine, and identifying a vibration sensor, the data for which correlates with the noise data in the region of interest. The method further comprises determining a threshold vibration level for the identified vibration sensor, the threshold being based on the vibration level detected by the identified vibration sensor in the region of interest, and adjusting one or more wind turbine operating parameters in response to the vibration level detected by the identified vibration sensor exceeding the threshold.

A double suction centrifugal fan capable of bidirectionally sucking fluid and a cooling apparatus for a computer using the same. In the centrifugal fan and the cooling apparatus, a disk is provided between blades and a hub so that fluid is sucked to both faces of the disk and then discharged toward the blades. That is, interference between sucked fluid is minimized to restrain creation of turbulence flow, thereby reducing noise and improving efficiency. Also inner ends of the blades of the centrifugal fan are arranged in an inner portion of the disk to relatively shorten the chord length of the blades, resultantly reducing tonal noise owing to BPF and thermal deformation of the blades. Furthermore, since the magnitude of the disk is adjusted, the number of the blades in not restricted and the centrifugal fan of the invention and the cooling apparatus mounting the centrifugal fan therein can be applied to computers by restructuring the frame and the cover of the cooling apparatus.

In various embodiments, methods, systems, and vehicles are provided for masking a tonal noise of a motor. In certain embodiments, a vehicle includes a drive system and an active masking acoustic signal generator (AMAG). The drive system includes a motor generating a tonal noise. The AMAG is configured to at least facilitate masking the tonal noise, by introducing a complementary harmonic tone, injecting dithering into the motor, or both.

A wind turbine having an attenuating unit is presented. One embodiment of the wind turbine includes a tower and a power unit disposed at a first end of the tower. The wind turbine further includes the attenuating unit that is operatively coupled to at least one of the tower and the power unit and configured to attenuate at least the portion of the vibrational bending waves having a frequency above a threshold frequency to reduce the tonal noise of the wind turbine.

A method of optimizing placement of a control source relative to a noise source includes establishing a first pool of constructive chromosomes, each constructive chromosome defining a potential spatial position for the control source in an acoustic space and each constructive chromosome including a plurality of constructive genes having a value-based value that represents an ordinate related to the potential spatial position. A second pool of constructive chromosomes is established by manipulating the value-based values of constructive genes from at least a portion of the plurality of constructive chromosomes of the first pool to create a plurality of modified constructive chromosomes, and evaluating a fitness characteristic of at least some of the constructive chromosomes from the first pool and / or at least some of the constructive chromosomes from the second pool. A portion of the constructive chromosomes are eliminated from the first and / or second pools based on the fitness characteristic.

A method of identifying an operating parameter of a wind turbine that contributes to the generation of tonal noise. The method comprises acquiring operating parameter data associated with a plurality of operating parameters of the wind turbine. The operating parameter data comprises a set of values for each operating parameter of the wind turbine. Noise data is also acquired that includes tonal noise produced by the wind turbine and is synchronised with the operating parameter data. The noise data is then binned with respect to a set of operating parameter values of a first operating parameter, and, for each of one or more of the bins, the noise data in the bin is analysed with respect to a set of values of a second operating parameter. The method then determines if there is a relationship between the second operating parameter and tonal noise produced by the wind turbine based on the analysis.

A method 400 of predicting tonal noise produced by a wind turbine is disclosed. The method comprises acquiring 410 a first set of vibration data, the first set of vibration data being from a plurality of vibration sensors positioned at different locations about a wind turbine drivetrain when the wind turbine drivetrain is undergoing testing in a test rig; acquiring 420 a second set of vibration data, the second set of vibration data being from a plurality of vibration sensors positioned at different locations about the same or a similar wind turbine drivetrain when located in a wind turbine; acquiring 430 noise data including tonal noise produced by the wind turbine; identifying 440 a vibration sensor of interest using vibration data of the second set of vibration data and the noise data; determining 450, for the identified sensor, a first relationship between vibration data of the first set of vibration data and the second set of vibration data; and determining 460, for the identified vibration sensors, a second relationship between the first set of vibration data and tonal noise produced by a wind turbine based on the first relationship.

The stationary housing of a conventional fan assembly is replaced with a rotating tip ring. The rotating tip ring has a shaped cross-sectional profile to enhance performance and eliminate tonal noise associated with the fundamental (or blade passing) frequency and its harmonics.

A method for of controlling audible levels of tonal noise produced by a wind power plant comprising a plurality of wind turbines is provided. The method comprises identifying a wind turbine as contributing to a level of tonal noise that is audible at a noise reception point; and adjusting one or more operating parameters of a wind turbine other than the identified wind turbine in order to reduce a level of tonal noise produced by the identified wind turbine that is audible at the noise reception point, and thereby reduce the level of tonal noise that is audible at the noise reception point. A controller configured to perform the method, a wind turbine and wind power plant comprising the controller, and a computer program which when executed by a computing device cause the computing device to perform the method, are also provided.

A method and apparatus for reducing a selected tonal noise generated by an axial flow fan operating in a non-uniform flow by locating at least one obstruction in the non-uniform flow such that the at least one obstruction generates a noise that is out of phase with the selected tonal noise. The noise generated by the at least one obstruction interferes with the selected tonal noise, thus reducing the selected tonal noise. It is also contemplated to use additional obstructions to reduce other tonal noises generated by the axial flow fan.

A method of analyzing wind turbine noise is provided. The method comprises acquiring noise data representing noise produced by a wind turbine and acquiring data from a plurality of vibration sensors positioned at different locations about the wind turbine. The method further comprises identifying a region of interest in the noise data, the region of interest being a candidate for containing tonal noise generated by the wind turbine, and identifying a vibration sensor, the data for which correlates with the noise data in the region of interest. The method further comprises determining a threshold vibration level for the identified vibration sensor, the threshold being based on the vibration level detected by the identified vibration sensor in the region of interest, and determining when the vibration level detected by the identified vibration sensor exceeds the determined threshold.

Method and apparatus are disclosed for active sound desensitization to tonal noise in a vehicle. An example vehicle includes an electric motor, a microphone, speakers, and an active sound desensitizer. The active sound desensitizer (a) randomizes channels of the speakers based on multiple uncorrelated broadband sound profiles, (b) determine upper and lower frequency band limits for a band-limitedfilter, (c) generate a desensitizing sound based on the upper and lower frequency band limits and the randomized channels, and (d) broadcast the desensitizing sound via the speakers.

A method controlling a wind turbine to avoid tonal noise production is provided. The method comprises acquiring (510) noise data representing noise produced by a wind turbine and acquiring (520) datafrom a plurality of vibration sensors positioned at different locations about the wind turbine. The method further comprises identifying (530) a region of interest in the noise data, the region of interest being a candidate for containing tonal noise generated by the wind turbine, and identifying (540) a vibration sensor, the data for which correlates with the noise data in the region of interest.The method further comprises determining (550) a threshold vibration level for the identified vibration sensor, the threshold being based on the vibration level detected by the identified vibration sensor in the region of interest, and adjusting (560) one or more wind turbine operating parameters in response to the vibration level detected by the identified vibration sensor exceeding the threshold.

A method 400 of predicting tonal noise produced by a wind turbine is disclosed. The method comprises acquiring 410 a first set of vibration data, the first set of vibration data being from a plurality of vibration sensors positioned at different locations about a wind turbine drivetrain when the wind turbine drivetrain is undergoing testing in a test rig; acquiring 420 a second set of vibration data, the second set of vibration data being from a plurality of vibration sensors positioned at different locations about the same or a similar wind turbine drivetrain when located in a wind turbine; acquiring 430 noise data including tonal noise produced by the wind turbine; identifying 440 a vibration sensor of interest using vibration data of the second set of vibration data and the noise data; determining 450, for the identified sensor, a first relationship between vibration data of the first set of vibration data and the second set of vibration data; and determining 460, for the identified vibration sensors, a second relationship between the first set of vibration data and tonal noise produced by a wind turbine based on the first relationship.

A method and apparatus of suppressing a vocoder noise are provided. The method includes receiving from a channel decoder a vocoder frame and first information, the first information indicating whether the vocoder frame has an error, generating speech data by performing voice decoding on the vocoder frame, determining whether a tonal noise has been detected in the speech data, if the first information indicates that the vocoder frame has an error, and attenuating the volume of the speech data and outputting the volume-attenuated speech data through a speaker, upon detection of the tonal noise in the speech data.