Abstract: A method and apparatus for signal prediction using the estimate-maximize ) algorithm in a time-varying signal system is provided. A time function is used to appropriately weight, in complementary fashion, the significance of both the complete and incomplete data sets used by the EM algorithm over a time period of interest. Initially, the EM solution is based solely on the complete data set. As time progresses, the significance of the complete data set in the solution decreases while the significance of the incomplete data set increases. By the end of the time period of interest, the EM solution is based solely on the incomplete data set. The rate of decrease of significance of the complete data set, and complementary increase in significance of the incomplete data set, are controlled by the characteristics of the time function.

Abstract: A method and apparatus for reducing drag and noise associated with fluid w within a conduit is provided. The conduit has flexible walls that are shaped to form stationary waves having peaks and troughs and are repeated in the axial direction of the conduit. The stationary waves are moved along the axial direction of the conduit whereby a vortex is trapped in the fluid flow at each of the troughs. Each of the vortices forms part of an isolating layer between the conduit wall and the main stream of the fluid flow thereby reducing drag. Furthermore, the vortices push the dominant noise producing region toward the center of the fluid flow where sound coupling efficiency is lower.

Abstract: An acoustic intensity probe was developed to measure waterborne sound intity levels using a two-hydrophone technique. The technique utilizes the cross-spectral density of signals from multiple closely spaced hydrophones. Planar (2-dimensional) and 3-dimensional arrays of hydrophones with symmetric and asymmetric configurations were developed to measure the acoustic intensity levels. This acoustic intensity probe combined with the two-hydrophone technique provides spcific information revelaing the acoustic energy distribution and propagation of noise sources in any acoustic environment.

Abstract: A cylindrical valve trim has holes in the valve trim wall that provide a fluid flow path through the valve. The holes pass through the wall at predetermined angles to create a plurality of counter-rotating vortices with parallel axes normal to the wall.

Abstract: A ring damper for reducing vibration and structureborne noise propagation piping systems, comprising a metal ring that is clamped circumferentially around the outer surface of the pipe or duct, said ring defining an annular chamber or cavity that is stuffed with a combination of damping materials.

Abstract: In a fluidborne or structureborne sound system, a method and apparatus are rovided for actively canceling transient acoustic noise. A high-speed controller utilizes a weighted combination of open and closed-loop inputs to provide a correction signal to a cancellation source. The cancellation source introduces a canceling acoustic wave that is equal in amplitude but 180.degree. out of phase with respect to the acoustic noise in order to cancel the acoustic noise within the system. The open-loop input is provided by a database containing a predicted, off-line model of the acoustic noise. The closed-loop input is provided by a combination of 1) an input signal generated by the input acoustic wave and feedback from the cancellation source as measured by an input sensor and 2) an error signal generated at the output of the system as measured by an error sensor. The weighted combination of the open and closed-loop inputs is chosen to minimize the error signal.