112 Proceedings of Indiana Academy of Science 



Comparing the result shown in figure 5 with that shown in figure 1, 

 it is seen that, by placing a locomotive whistle in a reflector in front 

 of the smoke stack the intensity of sound along the track in front of the 

 locomotive was increased to four times its value when the whistle was 

 located in the position (W) shown in figure 1. In direction 2 the in- 

 tensity was five times as great. At the same time the intensity at 

 right angles to the locomotive was correspondingly decreased. The 

 maximum intensity could have been changed from direction 2 to 1 by 

 rotating the whistle in the reflector. No doubt the multiplying factor 

 could be further increased by using a single tone whistle instead of 

 a chime whistle, and by making the reflecting surface of a material 

 having a higher reflection coefficient than plaster pai'is. In fact, the 

 writer has made the experiment and will publish his results in a later 

 paper, along with the results of his experiments on other phases of 

 the whistle problem. 



The placing of a locomotive whistle inside a reflector with its longi- 

 tudinal axis parallel to the axis of the reflector has advantages other 

 than those already noted. One is, that all parts of the circular steam 

 jet function, which is not the case when the whistle is mounted vertically 

 and the locomotive is running at high speed. This point was investi- 

 gated by placing a locomotive whistle in a stream of air from a compres- 

 sor capable of delivering 4,000 cubic feet of air per minute at a pressure 

 of 100 pounds to the square inch. The stream of air was adjusted to 

 give air velocity at the whistle of 20, 40, and 60 miles per hour. Very 

 little eff'ect was noticed at 20 miles per hour. At 40 miles per hour the 

 front portion of the whistle (the part against which the air current 

 was directed) functioned rather poorly, the volume of the sound being 

 considerably less than at 20 miles per hour. At 60 miles per hour 

 it did not function at all, nothing but the hissing .sound of escaping 

 steam coming from this portion of the whistle. As the whistle was 

 rotated the character or quality of the sound changed noticeably as one 

 after another of the several tones of the chime was silenced. The 

 steam jet whose vibiations about the lip of the whistle produce the 

 sound, must strike that lip in a particular way to give the best result. 

 When a locomotive is running at high speed the head on pressure and 

 the air currents about the sides of the whi.stle deflect the steam jet so 

 that some portions of it function poorly and others not at all. When 

 the whistle is inside a reflector the body of air about it is carried along 

 with it and the pressure is uniform on all sides of the jet. This per- 

 mits it to function normally at all speeds. 



All the information the writer has been able to get from psycholo- 

 gists and others is to the eff'ect that the average human ear is more 

 sensitive to sounds of from 1,000 to 1,200 vibrations per second than to 

 those of lower frequency. It would appear, therefore, that most loco- 

 motive whistles are from one to two octaves too low in pitch. Raising 

 the pitch would mean smaller whi.stles, smaller reflectors, less steam con- 

 sumption, and slightly less diff"raction loss. 



It would seem that the cost of whistle blowing is an item that 

 has been given little attention. A little consideration will convince 

 one that we "pay dearly for the whistle". 



