Abstract: A spectral subtraction noise suppression method in a frame based digital communication system is described. Each frame includes a predetermined number N of audio samples, thereby giving each frame N degrees of freedom. The method is performed by a spectral subtraction function H(w) which is based on an estimate of the power spectral density of background noise of non-speech frames and an estimate .PHI..sub.x (w) of the power spectral density of speech frames. Each speech frame is approximated by a parametric model that reduces the number of degrees of freedom to less than N. The estimate .PHI..sub.x (w) of the power spectral density of each speech frame is estimated from the approximative parametric model.

Abstract: An electric wheel-drive for motor vehicles, particularly automobiles with internal combustion engine, which can be installed nondestructively-reversibly in place of the brakes, with brushless, polyphasic, electronically speed-controlled electric motors individually attached to the wheels. The electric motor is a homopolar multiple-airgap axial-field motor whose rotor (1) replaces the wheeldrum and brake-disk, and whose stator (2) replaces the brake-shoes, brake-pads, and brake splash-shield plate of at least two wheels of a pair, in a conventional automobile with internal combustion engine. An electronic control system is included for the control of the axial-field motor during propulsion and braking. This electric wheel-drive allows for a fast, uncomplicated, and inexpensive hybridization of the car without modifications of the wheels, or the axle, or of other parts of the car, thereby providing the car with second, independent, propulsion system.