Abstract: A corrugated structure is designed by dividing a given length of a corrugated structure into a number of sections, or corrugations. The length is then divided by the number of sections to obtain a constant value which serves as a reference point for determining the varied pitches of the structure of the present invention. The varying pitch of each section is determined by adding or subtracting a variation value from the constant value to obtain a varying pitch. The variation values, and thus the varying pitches, of the sections of corrugated structure are empirically chosen. Whistles, or pure tones of noise, produced by the flow of a fluid relative to the corrugations are eliminated when the corrugated structure is designed according to three requirements: 1) the total of the pitches of a given section is approximately equal to the length of a given section; 2) no two adjacent sections can have the same pitch; 3) no two variations within a given set of sections can have the same value.

Abstract: A fluid distribution system, such as a valve, comprises a housing having a chamber which has a plurality of acoustic modes. The acoustic modes are excited when fluid flows through the chamber. An inlet passage and an outlet passage are disposed in fluid communication with the chamber. A plate is disposed in the inlet passage. A plurality of orifices are formed in the plate. The orifices conduct fluid from the inlet passage to the chamber and reduce the coupling between the flow of fluid through the inlet passage and the acoustic modes of the chamber. With this arrangement, the acoustic modes of the chamber and the resonance frequency of each of the orifices are substantially unexcited by the flow of fluid through the orifices.

Abstract: A silencer having multiple integrated channels arranged in a labyrinth configuration is provided. The channels have one open end and one closed end with the open end in communication with a common zone which is connected to a flow duct. The channels are tuned to provide a selected resonance frequency.

Abstract: A volumetric sound absorber for audible sound frequencies is made from a thin sheet material that is permeable to air with thickness mass, and flow resistance within specified ranges.

Abstract: A flow control valve installation having blind holes in internal surfaces. The holes are slanted in the downstream direction and tuned to null one or more frequencies in the noise spectrum for the valve by the selection of proper depths for the holes.

Abstract: A flow control valve having a flow-dividing cage surrounding its plug. The cage includes stacked plates spaced by dependent legs and annular screens in the spaces between adjacent plates.