Noise reducing apparatus of a cyclo-fan

Details Noise reducing apparatus of a cyclo-fan Noise reducing apparatus of a cyclo-fan

1995-02-02

1996-06-25

Isen, Forester W.

Electrical audio signal processing systems and devices

Acoustical noise or sound cancellation

Adjacent ear

415119, G10K 1116

Patent

active

055307663

ABSTRACT:
A noise reducing apparatus for a cyclo-fan is provided for the canceling of a whistling noise with a specific frequency, determined by the product of the rotation number of the cyclo-fan and the number of blades thereof. The apparatus comprises a cyclo-fan including a plurality of blades with arc shapes radially disposed centering the axis thereof, and a couple of supporting members for supporting both ends of the respective blade; a sensor for the passage of the respective blade at a fixed position; a controller for calculating the frequency and pressure level of a peculiar noise generated by the cyclo-fan based on the signal transmitted from the sensor, and then generating an electric signal corresponding to the interference sound having a reverse phase and same pressure level to that the peculiar noise, and a plurality of speakers for converting the electric signal from the controller into the interference sound. The controller calculates the frequency of the peculiar noise by multiplying the rotation number of the cyclo-fan and the number of blades. In addition, the pressure of the peculiar noise is determined in proportion to the interval between the cyclo-fan and the stabilizer for guiding air generated from the cyclo-fan. The latter may be previously given as a constant value.

REFERENCES:
patent: 4180329 (1979-12-01), Hildebrand et al.
patent: 4887087 (1989-12-01), Clearwater
patent: 5355417 (1994-10-01), Burdisso et al.

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