Boots – shoes – and leggings
Patent
1992-07-08
1994-05-10
Black, Thomas G.
Boots, shoes, and leggings
36455101, 364575, 340825210, 330149, G01H 700, G06G 712
Patent
active
053114469
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention concerns a signal processing system which can be used to monitor one substantially periodic component where there is interference from one or more other substantially periodic components. Each component is usually associated with a particular vibration source. The system may be incorporated in an active control system for reducing noise and in the resulting control system, is normally used one per source of vibration.
The signal processing system has input signals which are time-related to each of the periodic sources. These additional inputs allow improved rejection of the vibration from other sources.
In this application the term vibration is used to mean any vibration, such as the vibration of solids and the vibration of fluids, normally referred to as sound or velocity perturbation.
BACKGROUND INFORMATION
There have been many attempts to achieve noise reduction by the use of active control and there are many publications relating to these previous systems. Most have dealt with the control of a single source of unwanted vibration, while others have treated multiple sources as a single, more complicated source. For example, in the control of cabin noise in propeller driven aircraft, the individual propellers are separate sources which are physically separate and, since the engine speeds are not identical, not completely coherent. However, previous methods to control aircraft cabin noise, have considered the vibrating cabin walls as a single, distributed source. Vide Warnaka, G. E. & Zalas, J. M. "Active Attenuation of noise in a closed structure." UK Patent 2,132,053: Groves, H. W. "Noise Suppression." UK Patent 2,126,837: Nelson, P. A. & Elliott, S. J. "Improvements in or relating to active noise reduction." UK Patent 2,149,614.
Most active control systems use a measure of the residual vibration at a point where reduction is desired to adjust the actuator drives vide Chaplin, G. "Active attenuation of recurring sounds." UK Patent 1,577,322. This measure will be corrupted by noise, due either to extraneous "background" vibration or to electronic noise. The level of this noise will limit the performance of the control system. If the source of vibration to be controlled is periodic, or almost periodic, in nature then the process of synchronous averaging can be used to reject noise which is not harmonically related to the vibration source. A signal from the vibration source is needed to synchronize the averaging process. This may be a signal from a tachometer or an applied voltage or similar. If the noise is random in nature then the ratio of the signal power to the noise power is increased in proportion to the number of averages. However, if the noise is from another periodic source of not identical speed, the noise to signal ratio is an oscillating function of the averaging time. Reference is made to FIG. A of the drawings, in which the envelope decays only slowly and scales with the best period of the two periodic sources. Conventional active control means then adopt one of two strategies.
The first is to average for a sufficiently long time, compared with the beat period, so that the envelope of the noise to signal ratio has decayed to a small enough value.
The second is to treat the vibration as if it were coming from a single source. This requires the system to adapt on a time-scale short compared with the beat period.
The first method cannot be used if the signal, that is the unwanted vibration, is not constant for long enough. The second method fails if the two fundamental frequencies drift apart producing a very rapid beating.
SUMMARY OF THE INVENTION
In a system incorporating the invention separation of the signal from the noise can be achieved by averaging for just the right period of time so that the noise to signal ratio is at, or close to, a zero.
The invention also lies in a signal processing means which achieves this separation, and which is characterized by having at least two inputs (rather than the single input of a conventional system), so tha
REFERENCES:
patent: 3900823 (1975-08-01), Sokal et al.
patent: 4587620 (1986-05-01), Niimi et al.
patent: 4694415 (1987-09-01), Hasenkopf
patent: 4853686 (1989-08-01), Kueng et al.
patent: 4926361 (1990-05-01), Ohstubo et al.
patent: 4937769 (1990-06-01), Verbanets
patent: 4947356 (1990-08-01), Elliott et al.
patent: 5029118 (1991-07-01), Nakajima et al.
patent: 5136529 (1992-08-01), Makie et al.
patent: 5148402 (1992-09-01), Magliozzi et al.
Eatwell Graham P.
Ross Colin F.
Active Noise and Vibration Technologies Inc.
Black Thomas G.
Louis-Jacques Jacques H.
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