565 results about "Active noise control" patented technology

The technology of active noise reduction (ANR) is incorporated into audiometry testing in a variety of formats. Analog feedback, digital feedback, adaptive feedforward, and adaptive feedback noise control schemes are presented for use in audiometry to reduce the ambient noise heard by the test subject, allowing subject testing in higher ambient noise fields. Audiometer test signals are appropriately compensated so the test results are accurate and comply with existing calibration standards for audiometers. Existing audiometry headphone technologies are modified so that ANR can be accomplished while satisfying existing standards for audiometric testing. Embodiments are also defined for alternate headphone arrangements that may not conform to current (1997) audiometric testing standards but provide sufficient performance advantages to warrant new standards for audiometry testing in the future.

An active noise control (ANC) system may be implemented to both sides of a fan, such that both directions of the noise emitting are treated to reduce the overall noise. The impact on airflow is minimal, and the technique is very effective in a broad range of low frequencies. Passive sound-absorbing materials may be included for attenuation of high frequencies. The resulting quiet fan produces a low level of noise compared to any other device based on fan, which produces the same capacity of airflow. The quiet fan may be incorporated in any mechanical system which requires airflow induction such as: computers, air conditioners, machines, and more.

In an active noise reduction apparatus with an adaptive notch filter used, a triangle wave as a reference signal input into a first coefficient updater and a second coefficient updater reduces the number of execution times of product-sum operations in a reference signal generator to reduce the operation load.

The invention relates to a noise reduction device of a range hood. The noise reduction device is characterized in that a fan inlet is detachably provided with a lower noise-damping device; the lower noise-damping device comprises at least one noise-damping unit; the noise-damping unit comprises a longitudinally arranged noise-damping pipeline; the upper end of the noise-damping pipeline is communicated with the fan inlet, and the lower end of the noise-damping pipeline is communicated with the air outlet of a fume collecting hood; the air inlet end of the noise-damping pipeline is provided with a speaker, the inner wall of the noise-damping pipeline is provided with a reference microphone and an error microphone which is positioned below the reference microphone; and the reference microphone, the error microphone and the speaker are controlled by an active noise reduction controller. The noise reduction device disclosed by the invention can realize the noise reduction without improving the internal structure of the range hood but just by detachably arranging the lower noise-damping device on the fan inlet, the noise-damping device can be assembled and dissembled freely, so that good universality and adaptability are achieved, the problem of noise at the air inlet of the rang hood can be well solved, and the problem of noise of the air outlet of the range hood can be solved by detachably arranging an upper noise-damping device on a fan outlet.

The invention discloses a method and device for counteracting environment noise and an active noise reduction earphone. The device comprises a microphone, a DSP chip, an active noise reduction controller, and a loudspeaker, wherein the microphone is used as a feed-forward noise reduction microphone and an environmental noise monitoring microphone so as to acquire the environmental noise in real time; the DSP chip periodically selects a noise reduction mode best-matched with the current environment according to the environmental noise acquired by the microphone, and sending a corresponding noise reduction parameter to the active noise reduction controller; the active noise reduction controller performs the feed-forward filter noise reduction according to the noise reduction parameter sent by the DSP chip, and outputs the waveform for counteracting the environmental noise; and the loudspeaker plays the corresponding sound signal according to the waveform to counteract the environmental noise at the ear, thereby achieving the optimal noise reduction effect under various different environments, and the switching of the noise reduction mode is self-adaptively performed aiming at different noise environments, thereby guaranteeing that the best noise reduction experience can be provided under various different environments.

The invention relates to an active noise reduction system for an engine in an automobile. The system comprises two error microphones, five secondary sound source loudspeakers and one self-adaptation active controller. The two error microphones are arranged at automobile roof positions corresponding to a front row and a back row of the automobile. The five secondary sound source loudspeakers are composed of four vehicle-mounted loudspeaker boxes arranged on the automobile door sides and one secondary sound source arranged at the position of a rear row partition plate. The self-adaptation active controller comprises a DSP master control chip, an audio decoding chip, an off-chip storage unit, a CAN bus controller, a power amplifier, an error microphone signal receiving module, a secondary sound source output module and a power module. The invention further relates to an active noise reduction method for the engine in the automobile. By means of the system and method, error noise signals in active noise reduction reach the minimum value during constant noise reduction control, the noise influence caused by the error noise signals can be basically ignored, and the expected noise reduction effect can be rapidly achieved.