97results about How to "Reduce audible noise" patented technology

A dimmable, light-emitting diode (LED) power supply adapted to provide a direct current (DC), constant current (“constant current source”) from a conventional, phase-controlled 120 VAC, 60 Hz power source is disclosed. The constant current source of the present invention utilizes two processes to control dimming. In a first process, the phase angle of the input voltage is used to control the duty cycle of a line frequency pulse width modulation (PWM). In a second process, a proportional-current limit adjustment is used to control the average current to the LED during the ON time of the line frequency by PWM. As a result, at relatively low phase angles, peak currents can be lowered, reducing flicker and improving the audible noise levels generated by the circuit.

A disk drive is disclosed comprising a spindle motor comprising a plurality of windings for rotating a disk. The spindle motor is rotated by commutating the windings over a plurality of commutation states, wherein audible noise generated by the disk drive is reduced by phase modulating the commutation interval. Further audible noise reduction is achieved by modulating a current applied to the windings which substantially reduces discontinuities in the torque output of the spindle motor caused by phase modulation of the commutation intervals.

A portable ventilator for providing an air-recipient with compulsory respiration is provided with an outlet manifold and a single-expansion-chamber muffler configured so that airflow through an inhale outlet port of the muffler is pulse-free and a transmission loss, defined as the ratio of sound power generated by the at least one compressor and incident on the muffler to the sound power transmitted by the muffler, is sufficient to deaden the sound power of the compressor.

A dimmable, light-emitting diode (LED) power supply adapted to provide a direct current (DC), constant current (“constant current source”) from a conventional, phase-controlled 120 VAC, 60 Hz power source is disclosed. The constant current source of the present invention utilizes two processes to control dimming. In a first process, the phase angle of the input voltage is used to control the duty cycle of a line frequency pulse width modulation (PWM). In a second process, a proportional-current limit adjustment is used to control the average current to the LED during the ON time of the line frequency by PWM. As a result, at relatively low phase angles, peak currents can be lowered, reducing flicker and improving the audible noise levels generated by the circuit.

A variable voltage and frequency output wind turbine. Variations of the wind turbine include use of a slotless alternator to reduce alternator noise, a high power AC output to facilitate transmission of the output over extended distances, AC to DC converters and DC to AC converters, and sensors for systems and devices to receive the wind turbine output and to allow matching of the output to the receiving devices and system. Other features include a removable hatchcover for dissipating heat from components contained in the turbine or attached to the hatchcover, a swept blade design to reduce blade-produced noise, and power storage components for storing and intermittently using energy stored as a result of wind turbine power generation.

A fan control system and method that maintains the operating temperature of computer and electronic devices or components at about a predetermined control level to minimize power consumption and audible noise. The fan control system is a programmable closed loop system including a temperature sensor, first and second fan controllers, and a fan / motor assembly including a power converter, a motor, and a fan. The first fan controller provides programmable acceleration / deceleration of the fan during an initial fan spin up, and the second fan controller runs the fan only as fast as necessary to keep the sensed temperature level of a computer device as close as possible to the predetermined control level, thereby minimizing the power consumption of the system and the audible noise of the fan.

A wind turbine comprising at least a blade (11) having an aerodynamic profile with a leading edge (13), a trailing edge (15) and suction and pressure sides between the leading edge (13) and the trailing edge (15) that includes an anti-noise device (31) placed on the suction side formed by elements (33) that modify the frequency spectra of the boundary layer noise. Preferably the anti-noise device (31) is placed on the suction side between two sections corresponding to chord positions in the range of 40%-95% of -the chord length, measured from the leading edge (13).

A method of searching a plurality of Vector Quantization (VQ) codevectors for a preferred one of the VQ codevectors to be used as an output of a vector quantizer for encoding a speech signal, includes determining a quantized prediction residual vector, and calculating a corresponding unquantized prediction residual vector and the energy of the difference between these two vectors (that is, a VQ error vector). After trying each of the plurality of VQ codevectors, the codevector that minimizes the energy of the VQ error vector is selected as the output of the vector quantizer

A method of operating a brushless direct current motor is provided that generates a rotor position dependent pulse width modulation waveform. The waveform can improve motor efficiency and reduce torque variation.

A fan control system and method that maintains the operating temperature of computer and electronic devices or components at about a predetermined control level to minimize power consumption and audible noise. The fan control system is a programmable closed loop system including a temperature sensor, first and second fan controllers, and a fan / motor assembly including a power converter, a motor, and a fan. The first fan controller provides programmable acceleration / deceleration of the fan during an initial fan spin up, and the second fan controller runs the fan only as fast as necessary to keep the sensed temperature level of a computer device as close as possible to the predetermined control level, thereby minimizing the power consumption of the system and the audible noise of the fan.

The invention relates to a transmission line audible noise prediction method based on BP neural network optimization. The method includes acquiring and preprocessing data parameters, establishing a BP neural network prediction model of the data parameters, performing optimization training on the BP neural network by the ant colony algorithm, and utilizing the network to predict the transmission line audible noise. The method has high prediction accuracy, fine convergence and high stability, the problem that the BP neural network falls into local minima is avoided, and great guidance significance is provided for transmission line audible noise prediction and audible noise reducing development.

A system for damping audible noise from a drive train. One embodiment is a system with an audible noise signal from a drive train wherein a damping circuit produces a damping torque that is a phase shifted and amplified version of the noise signal that is applied to the air-gap torque of a generator or motor coupled to the drive train and effectively reduces the audible noise.

A method to denoise a stereo signal comprising a stereo sum signal and a stereo difference signal, performs a frequency selective stereo to mono blending based on the masking effect of the human auditory system. Therefore, a stereo signal noise reducer, comprising a first filter bank (1) to split the stereo difference signal (1−r) into a plurality of subbands, respective first multipliers (20, . . . , 2N) to weight each of the subbands of the stereo difference signal with a respective corresponding control signal (C0, . . . , CN), and a first adder (3) to sum all weighted subbands of the stereo difference signal (1−r) to build a frequency selective weighted stereo difference signal (diff), within which a number and width of the subbands obtained via the first filter bank (1) are choosen according to the properties of the human auditory system, further comprises a weighting factor determination unit which determines a respective control signal (C0, . . . , CN) frequency selective based on the masking effect of the human auditory system.

A system for damping audible noise from a drive train. One embodiment is a system with an audible noise signal from a drive train wherein a damping circuit produces a damping torque that is a phase shifted and amplified version of the noise signal that is applied to the air-gap torque of a generator or motor coupled to the drive train and effectively reduces the audible noise.

Acoustic vibrations generated by von Karman vortex streets are reduced by shaping members interposed in moving air flowstreams, such as fan guards and grilles used in forced flow air conditioning systems, to have either a cylindrical cross section or a non-cylindrical cross-section with non-linear or interrupted leading or trailing edges presented to the air flowstream. Relatively flat rectangular cross-section members with interrupted or non-linear leading or trailing edges formed by somewhat sawtooth or sinusoidal wave forms or connected to spaced apart support members, or cylindrical members formed in the shape of a sawtooth or sinusoidal wave form, or presented with spaced apart rings or grooves interrupting the cylindrical cross-section of the member are typical configurations which exhibit reduced or substantially eliminated acoustic vibrations caused by von Karman vortex shedding.

A system for performing a computationally efficient method of searching through N Vector Quantization (VQ) codevectors for a preferred one of the N VQ codevectors predicts a speech signal to derive a residual signal, derives a ZERO-INPUT response error vector common to each of the N VQ codevectors, derives N ZERO-STATE response error vectors each based on a corresponding one of the N VQ codevectors, and selects the preferred one of the N VQ codevectors based on the N ZERO-STATE response error vectors and the ZERO-INPUT response error vector.

Disclosed is a PFC (power factor correction) device for shaping an input current of a power converter. The device includes means for receiving a rectified input voltage derived from an AC input voltage; load determining means for determining a load value L which represents the power drawn by a load supplied by the power converter; current shaping means for shaping the input current of the power converter to follow a reference waveform; and control means for controlling the current shaping means to operate over a conduction interval α during each positive and negative half cycle of the AC input voltage. The duration of the conduction interval is controlled in accordance with the load value L. The current shaping means may shape the input current to follow the reference waveform which crosses zero at phase angles which substantially correspond to the start and end of the conduction interval.

A liquid crystal display (LCD) and a method of driving the LCD are provided. The LCD includes a display panel; and a timing controller providing a first data signal to the display panel during a first frame period, a second data signal to the display panel during a second frame period and a blank signal to the display panel during a blank period between the first and second frame periods, wherein the voltage of the blank signal varies among a plurality of levels between the voltage of the first data signal and the voltage of the second data signal.

A bicycle front derailleur includes a chain guide that is provided with a pushing element that is movable relative to the chain guide to assist in shifting a bicycle chain from a smaller front sprocket to an adjacent larger sprocket. The chain guide is part of a movable member that is movably coupled to a base member via a linkage assembly. The pushing element has a contact surface that preferably moves both laterally outwardly and longitudinally as the pushing element moves from a first position to a second position. Preferably, the pushing element is chain activated and arranged to move at least laterally outwardly by contacting a chain that is moving between inner and outer chain guide members of the movable member. Preferably, the pushing element is either a slidable member or a rotatable member.

A noise reduction apparatus can include a frame and multiple spaced apart panels positioned adjacent to each other. Each of the panels or only one of the spaced apart panel elements may have holes therein to receive acoustic waves for absorbing the waves between the panels. The panels can be attached to a frame or other connection structure so that the arrangement of panels can be hung over a work space or positioned in a work space (e.g. in a wall, formed as a partition or wall, included as part of shelving, etc.). The panels can also be incorporated into a light fixture that may hang from a ceiling or be attached to some other type of support (e.g. a table, a base, etc.). The panels can be composed of glass, wood, or other type of material.

A guitar effects pedal board with a multi effects switcher pcb assembly or assemblies encased in an effects pedal board which can activate or deactivate single or groups of multiple effects pedals which are set on top or mounted to the top of an effects pedal board. What is novel about this invention is that the multi effects switcher pcb assembly or pcb assemblies are integrated into the pedal board sheet metal and is not a separate product attached the pedal board. This design lends itself to a more cost effective solution for the consumer with easier initial setup when mounting and connecting cables between the multi effects switcher connections and the effects pedals connections, resulting in a more organized effects pedal board cable management system by minimizing cable cross over, audible noise and tone loss.

A bicycle front derailleur includes a chain guide that is provided with a pushing element that is movable relative to the chain guide to assist in shifting a bicycle chain from a smaller front sprocket to an adjacent larger sprocket. The chain guide is part of a movable member that is movably coupled to a base member via a linkage assembly. The pushing element has a contact surface that preferably moves both laterally outwardly and longitudinally as the pushing element moves from a first position to a second position. Preferably, the pushing element is chain activated and arranged to move at least laterally outwardly by contacting a chain that is moving between inner and outer chain guide members of the movable member. Preferably, the pushing element is either a slidable member or a rotatable member.

A bicycle front derailleur includes a base member, a movable member and a linkage assembly. The base member is configured to be fixedly coupled to a bicycle frame. The movable member has a chain guide portion. The linkage assembly is coupled between the base member and the movable member to move the chain guide portion between a retracted position and an extended position. The chain guide portion includes a chain guide element defining a chain path and a movable plate arranged to pivot about a pivot axis relative to the chain guide element in a see-saw movement.

A bicycle front derailleur includes a base member, a movable member and a linkage assembly. The base member is configured to be fixedly coupled to a bicycle frame. The movable member has a chain guide portion. The linkage assembly is coupled between the base member and the movable member to move the chain guide portion between a retracted position and an extended position. The chain guide portion includes a chain guide element defining a chain path and a movable plate arranged to pivot about a pivot axis relative to the chain guide element in a see-saw movement.

The present invention uses a discharge path to release the power stored in an output capacitor of a converting circuit when the time interval between two adjacent switching thereof is too long and may generate noises whose frequencies can be sensed by human ears. Hence, the present invention can keep the operating frequency of the converting circuit higher than a predetermined frequency and reduce the audio noise of the converting circuit.

Noise reduction for a switching amplifier system having a differential output stage and demodulator filter responsive to complementary PWM signals includes generating in-phase PWM signals and gradually adjusting their duty cycle between a low duty cycle and the full duty cycle of the complementary PWM signals, generating full duty cycle PWM signals and gradually shifting their relative phase between in-phase and out-of-phase; and in response to a turn-on signal, adjusting the in-phase PWM signals from low to full duty cycle and shifting the relative phase from in-phase to out-of-phase, and in response to a turn-off signal shifting the relative phase from out-of-phase to in-phase and adjusting the in-phase PWM signals from full to low duty cycle for maintaining balanced charge on the demodulation filter to reduce audible noise.

A wind turbine comprising at least a blade (11) having an aerodynamic profile with a leading edge (13), a trailing edge (15) and suction and pressure sides between the leading edge (13) and the trailing edge (15) that includes an anti-noise device (31) placed on the suction side formed by elements (33) that modify the frequency spectra of the boundary layer noise. Preferably the anti-noise device (31) is placed on the suction side between two sections corresponding to chord positions in the range of 40%-95% of the chord length, measured from the leading edge (13).

A liquid crystal display includes a voltage providing unit for providing a common voltage which is a direct-current (DC) voltage level in each of a plurality of first periods of time, in each of a plurality of second periods of time, and in each of a plurality of third periods of time, wherein each first period of time is separated from each second period of time by at least one third period of time, wherein the DC voltage levels in at least one first period of time, at least one second period of time, and at least one third period of time are different from each other.

A method of controlling a synchronous motor that may include windings and a power driving stage coupled to the windings, may include using a feedback loop including using a feedback circuit coupled to the windings to generate current feedback components, using current controllers for generating respective voltage signals, and using an anti-transform circuit for generating control signals for the power driving stage. Using the feedback loop may include generating additional compensation signals for compensating the control signals, and adding the additional compensation signals from the current controllers by one of generating the additional compensation signals as quadrature and direct voltage compensation signals and adding them to the voltage signals to generate compensated quadrature and direct signals, and supplying the compensated quadrature and direct signals to the power driving stage by providing the compensated quadrature and direct signals to the anti-transform circuit.