Abstract: An air extractor is provided for reducing wind throb in a vehicle. The air extractor includes a support having a first opening. A first flap is pivotally mounted to support frame in the first opening. The first flap is displaceable between a fully outwardly open position, a fully inwardly open position and an intermediate closed position. Further, the flap is tuned to a resonance frequency of between 12 and 18 hertz characteristic of the wind throb generated by the vehicle in which the air extractor is mounted.

Abstract: An air extractor is provided for reducing wind throb in a vehicle. The air extractor includes a support having a first opening. A first flap is pivotally mounted to support frame in the first opening. The first flap is displaceable between a fully outwardly open position, a fully inwardly open position and an intermediate closed position. Further, the flap is tuned to a resonance frequency of between 12 and 18 hertz characteristic of the wind throb generated by the vehicle in which the air extractor is mounted.

Abstract: A first major aspect of the invention relates to an active noise cancelling system which detects ambient noise and applies electro-accoustic processing thereto to produce an acoustic signal for cancelling out the ambient noise. The active noise cancelling system may be used to cancel all noise but an audio signal which is desired to be heard by the user. A second major aspect of the invention relates particularly to a system for electronically cancelling noise input to a user microphone, by utilizing known characteristics of speech signal and ambient noise. The first major aspect of the invention can be used in concert with the second major aspect in a communication system at the earpiece of a telephone and the mouthpiece of a telephone.

Abstract: A bilateral transducer (18) for use in an active noise cancellation system both senses ambient noise and produces acoustic waves to cancel the noise. The electrical interface for each bilateral transducer circuit consists of a speaker drive signal as an input and a simulated microphone signal as an output. In a first embodiment, the drive signal to the bilateral transducer is periodically turned off at a rate above audibility, and in the "off period" the transducer's drive element is sensed to produce a reverse output signal from which is subtracted a synthesized signal representing the speaker velocity response to the drive signal to produce the simulated microphone signal. In further embodiments, the reverse output signal is derived by sensing the energy being sent to the transducer to produce the acoustic waves, or by a separate sensing coil in a coil driven transducer.