Electrical audio signal processing systems and devices – Acoustical noise or sound cancellation – Acoustic – nonairborne vibration sensing or counterwave emission
Reexamination Certificate
1999-05-20
2001-01-23
Isen, Forester W. (Department: 2747)
Electrical audio signal processing systems and devices
Acoustical noise or sound cancellation
Acoustic, nonairborne vibration sensing or counterwave emission
C381S071110
Reexamination Certificate
active
06178246
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an active noise suppression of noise generated by a surface. At least one sensor such as a velocity sensor is connected to the noise radiating surface for providing a control signal that operates or controls an actuator that is effective on the surface to counteract the noise radiation.
BACKGROUND INFORMATION
Such a system is described, for example, in an article entitled “Active Control of Sound Radiation Using Volume Velocity Cancellation” by M. E. Johnson and S. J. Elliott, published in the “Journal of the Acoustic Society of America”, Vol. 98(4), October 1995. A velocity sensor is used which covers the entire surface that radiates the noise, just as the actuator for suppressing the noise also covers the entire surface. The velocity sensor measures only the uneven numbered vibration modes especially the base mode (
1
,
1
). The actuator only counteracts these base mode vibrations. If the noise radiating surface oscillates at higher vibration modes which have only one vibration component which is even numbered, for example (1,2)-, (2,3)-, etc., then such a integrating surface sensor no longer provides an output signal, because the integration of overall vibration or oscillation peaks and valleys yields a sum signal=0. However, it has been-noted, that the degree of radiation at such vibration modes of a vibrating or oscillating plate increases as the excitation frequency increases. These vibration modes include at least one uneven numbered component, for example (1,2)-; (1,3)-; (2,3)-; (3,3)-; etc. modes.
OBJECTS OF THE INVENTION
In view of the foregoing it is the aim of the invention to achieve the following objects singly or in combination:
to provide an apparatus for the active noise suppression capable of sensing and suppressing vibration or oscillation modes having at least one uneven numbered component;
to use sensor distribution patterns on the surface of a vibrating plate so that the desired active counteracting noise suppression is achieved; and
to use integrating sensors especially velocity sensors that have an axial sensitivity.
SUMMARY OF THE INVENTION
According to the invention an active noise suppression is achieved by controlling a noise suppressing actuator, that is effective on the noise generating surface, with a control signal generated by integrating sensors having an axial sensing selectivity, so that oscillations or vibrations are sensed in at least two directions crossing each other, preferably at a right angle in the (x, y) directions of a rectangular coordinate system.
Contrary to the prior art, the invention uses integrating sensors that are axially selective. Such sensors are preferably velocity sensors, or acceleration sensors, or deformation pick-ups, which are formed for example as piezo-film strips. As soon as a vibration mode having an uneven numbered component occurs along an axis of a surface covered with such a sensor the integrated sum signal provided by the sensor is no longer zero. As a result, the actuator controlled by the sensor signal can counteract the respective vibration mode of the plate. The arrangement of the sensors used according to the invention may assume various patterns described in more detail below, especially a rectangular coordinate matrix pattern.
REFERENCES:
patent: 4495434 (1985-01-01), Diepers et al.
patent: 5115472 (1992-05-01), Park et al.
patent: 5410607 (1995-04-01), Mason et al.
patent: 5651072 (1997-07-01), Nakao et al.
patent: 5812684 (1998-09-01), Steven
patent: 6031917 (2000-02-01), Mathur
patent: 3834853 (1990-04-01), None
The Journal of the Acoustical Society of America; vol. 98, No. 4, Oct. 1995, pp. 2174 to 2186.
Bebesel Marius
Maier Rudolf
Schmidts Klaus
Daimler-Chrysler AG
Fasse W. F.
Fasse W. G.
Isen Forester W.
Pendleton Brian Tyrone
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