Electrical audio signal processing systems and devices – Acoustical noise or sound cancellation – Counterwave generation control path
Reexamination Certificate
1996-10-22
2001-08-14
Harvey, Minsun Oh (Department: 2644)
Electrical audio signal processing systems and devices
Acoustical noise or sound cancellation
Counterwave generation control path
C381S071800
Reexamination Certificate
active
06275591
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to extracting component signals from a composite signal and, more specifically, to a method and assembly for extracting and identifying component signals from their responsive sources.
2. Description of the Related Art
There are many instances when it is desirable to analyze a signal. This is especially true in the automotive field when determining how much noise is going to be heard by the occupants of a motor vehicle. Depending on the level of noise, it is often a desire to reduce the noise to provide a motor vehicle with quiet operating characteristics.
Eliminating noise can best be accomplished by eliminating the source of the noise. Because noise, especially in motor vehicles, is a composite of many different noises, the source is often difficult to identify. Noise in motor vehicles is generated by its powertrain, the interaction between the road and the tire, and the wind it creates and drives through. These three types of noise have different characteristics and are, often times, random because they depend on so many variables which are also random. For example, the overall noise at a specific speed may have a substantially different characteristic if the powertrain is providing a substantial torque at that speed. Likewise, the overall noise may be affected by the condition of the road on which the motor vehicle is traveling. Therefore, there is a need to isolate the sources of the overall noise under various vehicle operating conditions to best eliminate it.
U.S. Pat. No. 5,419,198 to Pla discloses an electronic signal enhancement and separation assembly for machinery diagnostics. This assembly utilizes a sensor at each noise generator, namely a rotating shaft. In the embodiments contemplated by Pla, all of the noise generators were rotating shafts. The signals generated by the sensors were fed through an adaptive filter which modified itself based on the activity of the noise generator. This adaption allows the filters to more accurately identify the portion of the noise generated by each individual rotating shaft. This assembly only senses rotating objects, i.e., rotating shafts. Therefore, its usefulness is limited when used in an environment such as a motor vehicle. Although useful in detecting noise generated by a driveshaft, noise generated in a motor vehicle by other sources is random and an assembly that is capable of sensing periodic noise having a very small random component is not useful due to the time it takes to adapt to the randomness of the noise. More specifically, by the time the assembly adapts its filter to the noise in the motor vehicle, the motor vehicle will be in another condition generating a different type of noise for which the filter cannot adapt quickly enough. Therefore, there exists a need to adapt a filter quickly to react to the randomness of the signal it is filtering while accurately extracting the component of the noise signal for which it is designed.
SUMMARY OF THE INVENTION
Accordingly, an extracting assembly for extracting a component signal generated by a component source from a composite signal is disclosed. The extracting assembly includes a reference sensor that generates a reference signal relating to activity of the component source. A composite sensor senses the composite signal. An adaptive filter is operatively connected to the reference sensor and the composite sensor. The adaptive filter filters the component signal from the composite signal as a function of the reference signal generated by the reference sensor. A normalizer operatively connected to the adaptive filter normalizes the step size of each iteration taken by the adaptive filter to minimize the time to adapt the adaptive filter to transform the reference signal into the component signal.
One advantage associated with the present invention is the ability to adaptively filter a component signal and to extract same out of a composite signal. A second advantage associated with the present invention is the ability to adapt a filter in real time. Another advantage associated with the present invention is the ability to adapt a filter in real time in a rapidly changing environment. Still another advantage associated with the present invention is the ability to analyze components of a signal by filtering them out of the signal in the time domain rather than in the frequency domain.
Other advantages and features of the present invention will be readily appreciated as the same becomes better understood by reference to the subsequent description when considered in connection with the accompanying drawings.
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Burdisso Ricardo Anibal
Fuller Christopher Robert
Hollingsworth Larry Duane
Hsueh Keng D.
Lee Garland
Coughlin William J.
Ford Global Technologies Inc.
Harvey Minsun Oh
Mollon Mark L.
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