Method and apparatus for attenuating helical acoustic pressure waves

Claim 1

AN ACOUSTIC ATTENUATOR FOR USE WITH A HIGH SPEED, ROTARY FLUID MACHNE FROM WHICH IS EXHAUSTED A HIGH VELOCITY FLUID STREAM CONTAINING A HELICAL, AXIALLY ADVANCING, ACOUSTIC PRESSURE WAVE PATTERN INCLUDING RADIALLY TRAVELING PRESSURE WAVES; SAID ATTENUATOR COMPRISING: A RIGID, GENERALLY TUBULAR BAFFLE STRUCTURE HAVING A CENTRAL FLUID PASSAGE TO PASS SAID FLUID STREAM THERETHROUGH; SAID BAFFLE STRUCTURE COMPRISING A PLURALITY OF RIGID, RADIALLY DIRECTED BAFFLES CIRCUMFERENTIALLY SPACED ABOUT AND EXTENDING LONGITUDINALLY OF SAID PASSAGE AND RELATIVELY FLAT, RIGID OUTER WALLS JOINING ADJACENT BAFFLES ALONG THEIR RADIALLY OUTER EDGES, EACH BAFFLE INCLUDING A RELATIVELY FLAT, RIGID RADIALLY INNER EDGE FACE AND RELATIVELY FLAT, RIGID RADIALLY DIRECTED SIDE WALLS; THE SPACES BETWEEN ADJACENT BAFFLES BEING CLOSED ALONG THEIR RADIALLY OUTER SIDES BY SAID OUTER WALLS AND BEING OPEN ALONG THEIR RADIALLY INNER SIDES TO SAID FLUID PASSAGE, AND THE CIRCUMFERENTIAL WIDTH OF THE INNER OPEN SIDES OF SAID SPACES BEING SUBSTANTIALLY EQUAL TO THE CIRCUMFERENTIAL WIDTH OF SAID INNER BAFFLE FACES; AND THE RADIAL DIMENSION OF AT LEAST SOME OF SAID SPACES AT POSITIONS SPACED THEREALONG, MEASURED RADIALLY BETWEEN THE OUTER WALL OF THE RESPECTIVE SPACE AND THE INNER EDGE FACE OF AN ADJACENT BAFFLE, BEING SUBSTANTIALLY EUAL TO N$/4 WHERE N IS AN ODD INTEGER AND $ IS THE PREDETERMINED WAVELENGTH OF A RADIAL PRESSURE WAVE WITHIN SAID FLUID STREAM.