TRACING GRAMOPHONE AND PHONOGRAPH RECORDS. 33 



of curve in the figure ; there is a curious resemblance of the vibrations to 

 those of vowel curves. In the band curve (figure 31) we can pick out the 

 strong vibrations for the note on which most of the instruments coincide. 

 We notice that every fourth vibration is especially strong; it is from the 

 bass instruments playing two octaves below. The ver>^ short vibrations, 

 which can be detected best at a positive or negative apex, are from a piccolo. 

 The curve in figure 32 is from the record of a note from an orchestra. 

 The most prominent vibration is one whose wave-length is 3mm. = 0.0012s., 

 that is about the note gf^*. Another prominent feature is the grouping of 

 these vibrations in threes, indicating a tone with a period of 9mm. = 

 0.0036s., or a note about c'*. The greater strength of certain vibrations 

 indicates the presence of bass notes. There is one which reinforces every 

 sixth vibration of the high note and another that coincides approximately 

 with every ninth; the former would correspond to c"*, the latter to g~^^. 

 The combination of all these notes — each comprising a fundamental with 

 overtones — produces a very complicated curve. From such vibrations, 

 however, the ear can pick out not only the component notes but also the 

 characteristic tones of the piano, vioUn, etc. 



The record of the gong in figure 33 shows the effect of a blow. It 

 begins with a sudden upward deviation due to the blow of the hammer 

 and an ahnost complete vibration of smooth form before the gong begins its 

 special vibrations. The longer vibrations with a period of 7mm. = 0.0024s., 

 or about </'*, correspond to the lower tone of the gong, the shorter ones with 

 a period of 1. 3mm. = 0.0005s., or about c*, to the higher tone. The form of 

 the long wave shows that other prominent vibrations are jiresent. The 

 interference of the chief tones of the gong produces the beats seen in the 

 weaker portions of the curve. These beats occur every 60mm. = 0.0240s., 

 or about 40 times a second. Beats are heard in nearly all tones from 

 bells and gongs, but here they are not audible; this is due to their fre- 

 quency, which is sufficient to produce the impression of a low tone instead 

 of beats. 



The record of the conductor's whistle in figure 34 shows the very 

 short vibrations for the high note and also the pseudobeats (periodic 

 weakenings of the sound) that are produced by the rattling of the little 

 ball in the whistle; only a very small portion of the long record is given. 



Figure 35 gives a small piece out of the record of a European locomo- 

 tive whistle; the tone is not excessively high; it has a hollow character, 

 somewhat Uke that of a tuning-fork. 



The first of the three locomotive puffs in figure 36 was soft and long; 

 only a small piece is reproduced; its pitch was comparatively high and 



