196results about How to "Reduce low frequency noise" patented technology

The present invention relates to an audio signal controller adapted to receiving first and second digital audio signals and estimating a signal feature of the first or second digital audio signal. The estimated signal feature is compared with a predetermined feature criterion and the audio signal controller switches from conveying the first digital audio signal to conveying the second digital audio signal to a controller output, or vice versa, at a zero-crossing of the first digital audio signal or the second digital audio signal based on the comparison between the estimated signal feature and the predetermined feature criterion.

A gas turbine engine combustor defining a combustion zone therein and being adapted for receiving compressed air from a compressor. The combustor comprises inner and outer walls spaced-apart by a predetermined spacing distance and defines a cavity therebetween. The outer wall has a first area defining at least an impingement aperture therein, the impingement aperture permits fluid flow communication between the compressor and the cavity. The inner wall has a second area corresponding to the first area and defines a plurality of effusion apertures therein, the effusion apertures permitting fluid flow communication between the cavity and the combustion zone, and each of the effusion aperture defines a cross-sectional area smaller than that of the impingement aperture. The effusion apertures are disposed in groups having a predetermined geometric arrangement relative to the impingement aperture and define a ratio of number of effusion apertures to the impingement aperture of between about 2:1 and about 4:1. The combustor thereby provides damping of audible frequencies less that about 1600 Hz passing therethrough.

A circuit and method for reducing noise in video imagers which takes advantage of the fact that the same image information is present in the drain current in a reset transistor used to reset a photodiode in a pixel as is present in the readout current. The noise is reduced by passing the multiplexed output voltage from the source follower output transistor in an APS imager system through a high pass filter to reduce the low frequency noise from the source follower. The drain current in the reset transistor used to reset the APS is passed through a low pass filter. The low pass filter output and the high pass filter output are then combined. Since the drain current in the reset transistor contains the same image information as the voltage output of the source follower output transistor the image information can be obtained by combining the output of the low pass filter and the output of the high pass filter. Since the low frequency noise components of the source follower output transistor have been suppressed combined outputs of the low pass filter and high pass filter will provide the image information with greatly suppressed low frequency noise.

Pixels in a window, which corresponds to the position of an input pixel and has a predetermined size, are extracted from a reduced image obtained by reducing an input image to a predetermined scale. Substitute data used to substitute the value of the input pixel is generated based on the extracted pixels in the window. The difference value between the substitute data and input pixel value is calculated and is compared with a first threshold value. When the difference value is smaller than the first threshold value, the input pixel value is substituted by the substitute data. Thus, low-frequency noise reduction can be attained using a minimum required memory size while suppressing adverse effects such as a resolution drop and the like.

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

A centrifugal blower with forward curved fan blades includes an inlet shroud whose shape is specifically designed for creating a smooth incoming airflow pattern that leads into the inner leading edges of the fan blades. The inlet shroud has first and second curved surfaces, wherein the centers of curvature of the two surfaces lie in the same plane, and the center of curvature as well as the radius of curvature of one curved surface is greater than that of the other. At least one center of curvature lies beyond the outer diameter of the impeller, and at least one center of curvature lies beyond the impeller's inner diameter, wherein the impeller's inner diameter is defined by the inner leading edges of the fan blades. Performance benefits are achieved when a forward curved blower with such an inlet shroud operates with a flow coefficient of between 9 and 52.

In a predetermined range from a nose portion toward a scroll finish side in a scroll casing of a centrifugal blower, a first clearance dimension on a side of a suction port between an outer periphery of a centrifugal fan and a side plate of the scroll casing is set smaller than a second clearance dimension on a side opposite to the suction port between the outer periphery of the centrifugal fan and the side plate of the scroll casing. In addition, in the vicinity of the nose portion, a first wall part of the scroll casing on the side of the suction port protrudes toward a scroll finish side, from a second wall part of the scroll casing on the side opposite to the suction port.

A ventilating and noise-reducing apparatus for an indoor transformer is disclosed. The ventilating and noise-reducing apparatus comprises a ventilating louver and an axial flow fan used for performing ventilation and thermal dissipation to ensure a safe and stable operation of the indoor transformer, a multi-channel active control system used for the ventilating louver and mounted on the exterior of the ventilating louver, and a single-channel or multi-channel active control system used for the axial flow fan and mounted on the exterior of the axial flow fan. Due to the ventilating louver and the axial flow fan, the ventilation and thermal dissipation of the indoor transformer are ensured; and meanwhile, due to the active control systems, noise generated by the indoor transformer is restrained from radiating to the outside from the ventilating and thermal dissipating channels.

A calculated vertical velocity sensor signal is determined from a recorded pressure sensor signal. A constructed vertical velocity sensor signal is determined as a linear combination of the calculated vertical velocity sensor signal and a recorded vertical velocity sensor signal in dual-sensor seismic streamer data, using a mixture coefficient as a proportionality constant. An upgoing pressure wavefield component is determined as one half of a difference of the recorded pressure sensor signal and the constructed vertical velocity sensor signal, as a function of the mixture coefficient. An error in the upgoing pressure wavefield component is determined by propagating errors in the recorded pressure sensor signal and constructed vertical velocity sensor signal terms. A value of the mixture coefficient is determined that minimizes the error in the upgoing pressure wavefield component.

A noise reduction device used on rebreather is prepared as setting spiral air passage at internal of said device, arranging air inlet at external end of said air passage and air outlet at internal end center of said air passage, setting round arc-surface structure on side wall of spiral air passage and convex shoulder between side wall top-edge and air inlet. The said noise reduction device is installed at air inlet of fan on rebreather.

A noise suppression system reduces low-frequency noise in a speech signal using linear predictive coefficients in an adaptive filter. A digital filter may update or adapt a limited set of linear predictive coefficients on a sample-by-sample basis. The linear predictive coefficients may be used to provide an error signal based on a difference between the speech signal and a delayed speech signal. The error signal represents an enhanced speech signal having attenuated and normalized low-frequency noise components.

The invention discloses an anti-slip control method for a new energy automobile. The method comprises the steps that a vehicle control unit judges whether a vehicle has slip information or not according to a gear signal, a hand brake signal, a foot brake signal and whether a brake system has a fault or not; and if the slip information exists, the vehicle control unit sends an anti-slip instructionto a motor controller to enter a slope parking mode, wherein the slip information is that the rotating direction of a motor is opposite to the driving gear requirement and the rotating speed exceedsa set threshold value. By the adoption of the technical scheme, force is given in advance, the backward sliding distance is shortened, meanwhile, the slope sliding speed is reduced, and the safety performance of the vehicle is improved; and low-frequency noise during slope parking is reduced, and more comfortable riding subjective feeling is brought to passengers.

The invention discloses a self-adaption noise reduction device for low frequency noise in an indoor environment. The self-adaption noise reduction device for low frequency noise in the indoor environment comprises a primary microphone, an inverse sound source, a frequency adjusting device and a secondary microphone. The secondary microphone is a high-sensitivity omnidirectional electret secondary microphone with the response frequency ranging from 20Hz to 20KHz. The primary microphone and the secondary microphone are connected through an audio cable and a 16-bit analog-to-digital converter respectively. The 16-bit analog-to-digital converter is connected with an I/O read-write parallel interface of the frequency adjusting device through a 16-pin parallel interface bus. The reverse sound source is connected with an MCU processor of the frequency adjusting device through a serial analog-to-digital converter. The self-adaption noise reduction device for low frequency noise in the indoor environment is particularly suitable for low frequency noise processing in a household environment, low frequency noise emitted by indoor electronic devices and electrical devices can be obviously reduced, the living environment is improved, and the living quality is improved. The self-adaption noise reduction device for low frequency noise in the indoor environment is small in size, capable of being used once a system is powered, free of a complex installation process, low in manufacturing cost and capable of being completely purchased and deployed by general users.

An image processing method for reducing noise of an image to be filtered; the method includes a step of creating shrunken image of shrinking ratio r×r (where r is a natural number) by averaging the pixel values for each pixel in a block for every r pixels, a step of obtaining the pixel value in the shrunken image that correspond to the focus pixel in the source image by performing linear interpolation from the shrunken image pixels, a step of determining the noise reduction filter from the focus pixel and reference pixel in the shrunken image, and a step of computing the compensated pixel value of the focus pixel in the source image by weighted sum of each pixel value applying the filter to the focus pixel in the source image and the corresponding shrunken pixel.

The invention discloses a motor and a compressor with the motor. The motor comprises a stator and a rotor. The rotor is rotatably arranged inside the stator, the outer circumferential surface of the rotor is provided with a plurality of downward concave parts which are arranged at intervals in the circumferential direction of the rotor, protruding parts are formed between every two adjacent downward concave parts, and each protruding part is in transition with the downward concave part adjacent to the protruding part through a step part. According to the embodiment, the motor has the advantages of being low in noise, simple in structure, efficient in performance, easy to manufacture, capable of being produced in batches and the like.