50 l Prof. A. M. Mayer's Researches in Acoustics. 



more intense sound higher (instead of lower) in pitch. In 

 this ease, when the ear decides that the sound of the (lower 

 and feebler) tuning-fork is just extinguished, it is generally 

 discovered on stopping the higher sound that the fork, which 

 should produce the lower sound, has ceased to vibrate. This 

 surprising experiment must be made in order to be appre- 

 ciated. I will only remark that very many similar experi- 

 ments, ranging through four octaves, have been made, with 

 consonant and dissonant intervals, and that scores of different 

 hearers have confirmed this discovery. It is important to 

 understand that this phenomenon depends solely on difference 

 of pitch, and not at all on the absolute pitch of the notes. 

 Thus a feeble d" (1024 double vibrations) is heard as di- 

 stinctly through an intense e'" (1280 double vibrations) as a 

 feeble c (128 double vibrations) is heard through an intense 

 g (192 double vibrations) or an intense cf (256 double 

 vibrations). 



The development of the applications and of the further 

 illustrations of these discoveries would occupy too much space ; 

 I must therefore restrict myself to mentioning some of the 

 most interesting. Let a man read a sentence over and over 

 again with the same tone and modulation of voice, and while 

 he is so doing forcibly sound a c' pipe (256 double vibrations), 

 A remarkable effect is produced, which varies somewhat with 

 the voice experimented on; but the ordinary result is as follows. 

 it appears as though two persons were reading together, one 

 with a grave voice (which is found by the combination of all 

 the reader's real vocal sounds below c in pitch, or having less 

 than 256 double vibrations), the other with a high-pitched 

 voice, generally squeaky and nasal, and, I need not add, very 

 disagreeable. Of course the aspirates come out with a dis- 

 tressing prominence. I have observed many curious illus- 

 trations of this change in the quality of the tone of the voice, 

 caused by the entire or partial obliteration of certain vocal 

 components, while listening to persons talking during the 

 sound of a steam whistle, or in one of our long, resonant 

 American railway carriages. Experiments similar to those 

 on the human voice can be made, with endless modifications, 

 on other composite sounds, as those of reed-pipes, of stringed 

 instruments, of running water, &c. With one of my c (128 

 double vibrations) free Grenie reeds, I get very marked re- 

 sults. Using as a concurrent sound an intense c' (256 double 

 vibrations), I perceive the prime or fundamental simple tone c 

 to be unaffected in intensity, while all the other partial tones 

 (higher harmonics or overtones, as they are sometimes called) 

 are almost obliterated, except the fifth partial (or fourth upper 



