A Note on the Silencing of Air-stirring Motors

Abstract

Air-stirring motors are often viewed with disparagement in the laboratory because of the rather large amount of noise which attends their use. This noise may be traced to four sources: (1) that arising from the turbulent discharge of air from· the compressed air lines into tubing connecting with the motor; (2) that due to air rushing through the pipes and the connecting tubing; (3) that inherent in the use of an air motor, i.e. bearing noise and the clear tone of audio-frequency which is associated with all turbines; and (4) that resulting from the air rushing out of the small escape ports generally provided in the flat surface on top of the motor. Of these sources, the first and fourth are by far the most important because of both the intensity and the raucous character of the noise arising from them. The devices suggested here have been found very useful in reducing to a very large extent the noise from these two sources. The second and third sources enumerated are of smaller importance, but their contribution to the total noise may be minimized by suitable choice of connective tubing and by judicious oiling.