in void 40 the other portion of the fluid passes through perforations 36 into fill pack 32 and through the interstitial spaces around particles 38 like fill pack 20 fill pack 32 acts like a flow resistor flow of the fluid through fill pack 32 dissipates the already reduced linear speed of the flowing fluid and attenuates the noise of the fluid even more part of the fluid in fill pack 32 passes into void 40 before exiting housing 12 part of the fluid exits fill pack 32 at the top thereof without passing into void 40 and part of the fluid may pass back into void 42 before flowing through the open end of housing 2 it should be understood that plate 26 may have openings or perforations along the portion of plate 26 that jointly borders fill packs 20 and 32 the high flow resistance of fill pack 32 compared to the low flow resistance of void 42 ensures that substantially all of the fluid flowing into fill pack 20 will flow into void 42 before flowing into fill pack 32 in fact the portion of plate 26 jointly bordering fill packs 20 and 32 may be eliminated altogether without substantially affecting the sound attenuating operation of the device this feature is shown in fig7 fig2 shows the operation of the preferred muffler embodiment during a higher than normal surge of pressurized fluid higher fluid pressure acting against plate 26 and obstruction 46 will raise plate 26 and.