PatentDOI
Aircraft cabin noise control apparatus
TLDR
In this article, the phase relationship between a reference propeller or fan and some or all of the other propellers or fans is adjusted dynamically during flight to minimize propeller noise in the cabin over a range of flying conditions.Abstract:
In propeller of fan driven aircraft, cabin noise levels may be reduced by adjustment of the phase relationship between a reference propeller or fan and some or all of the other propellers or fans. An aircraft cabin (1) contains four microphones and two loudspeakers which form the active elements of a noise control system. The microphone outputs are fed via amplifiers to a digital signal processor (11) having an adaptation algorithm in a memory store. The processor generates an error signal which is used to adjust the synchrophase angle between the reference propeller and a synchrophased propeller, controlled by a synchrophaser. Thus the synchrophase angle is varied dynamically during flight to minimize propeller noise in the cabin over a range of flying conditions.read more
Citations
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PatentDOI
Noise cancellation apparatus
Douglas Andrea,Martin Topf +1 more
TL;DR: In this article, the authors propose an approach for reducing acoustic background noise for use with a telephone handset (10) or a boom microphone device (100) or an audio boom headset (401) or the like.
PatentDOI
Adaptive noise cancellation and speech enhancement system and apparatus therefor
Douglas Andrea,John M. Kowalski +1 more
TL;DR: In this article, a headset apparatus for use in an intercommunications system, the headset suppressing both noise in the vicinity of a transducer delivering sound to an operator's ear and in outgoing speech from the operator.
PatentDOI
Active vibration control.
TL;DR: In this article, two loudspeakers are driven by signals derived from a reference signal x(n) by adaptive filtering carried out by a programmed microprocessor and memory unit, which adapts the filtering in dependence on error signals el(n), from four microphones (421, 422, 423 and 424) distributed in the passenger compartment.
Patent
Quiet zone control system
Duane Wertz,Vasant Shridhar +1 more
TL;DR: In this paper, an adaptive filter having filter coefficients is used to generate an anti-noise signal to drive a speaker to produce sound waves to destructively interfere with an undesired sound in a quiet zone.
Patent
Noise suppression system
TL;DR: In this article, a noise cancellation system comprising a symmetrical assembly (24, 26) of microphone inputs is disclosed. And the controller (46) receives the output of the microphone assembly (49, 50) and generates an electrical cancellation signal having a polarity opposite the polarity of a portion of a noise to be cancelled and a magnitude equal to the magnitude of the portion of the noise being cancelled.
References
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PatentDOI
Apparatus and method for global noise reduction
TL;DR: In this article, an attenuating sound radiated from a vibrating surface into a control volume is described as comprised of a source of a control signal indicative of the amplitude and frequency content of the sound transmitted from the vibrating surfaces.
Patent
Noise cancellation apparatus
TL;DR: In this article, an array of independent sound cancellation units is arranged over a vibrating noise generating surface, each unit includes an arrangement of acoustic transducers (sensors) positioned adjacent the surface to obtain an electrical average of the local acoustic noise generated by a predetermined zone of the surface.
PatentDOI
Active noise control system
TL;DR: In this article, an active noise control system reduces cabin noise levels for a propeller or propfan aircraft by making the output from a secondary noise source identical in amplitude but opposite in phase to the propeller noise signature.
PatentDOI
Attenuation of sound waves
TL;DR: In this article, an active sound control system is described in which allowance is made in a relatively uncomplicated circuit for acoustic coupling between a sound generating system for generating a cancelling sound wave and a detector for sensing a sound wave to be cancelled.
PatentDOI
Improved method of an apparatus for cancelling vibrations from a source of repetitive vibrations
TL;DR: In this article, primary vibrations from a repetitive source of such vibrations are nulled in a location by specially generated secondary vibrations fed to the location from an actruator, where the actuator is driven by a waveform generator which is synchronized to the source by a synchronizing signal on the line which is derived otherwise than from the source.