Abstract: An auger construction is provided which reduces the surface noise radiated by the auger and serves to at least partially isolate the auger from the remainder of the machine. The auger construction comprises an inner shaft and outer concentric shafts, the latter carrying the helical cutting blade and generally corresponding to the shaft of a conventional auger. An elongated annulus of noise and vibration dampening material is disposed between the inner and outer shafts. Preferably, the outer shaft is isolated from the machine by further noise dampening material disposed between the mounting flange and the proximate end of that shaft and between the free end of the inner shaft and the end of the hose in the outer shaft. A bore in the inner shaft is also filled with noise dampening material. A number of arrangements are disclosed for fixing the two shafts together so as to prevent rotational slippage therebetween.

Abstract: Means and methods for prevention of undesirable acoustical whistles in mufflers or silencers of inexpensive and convenient design are shown. The broad inventive concept is that of preventing extended smooth flow of gas within a perforated tube, and this is taught by regular or random beading, by internal banding, or by provision of a screen structure for insertion within the tube.