65 ON THE MECHANISM 



to the ear, such as the report of a gun, the wash of waves on the 

 beach, &c. Sounds are produced by regular vibration of the 

 elastic air, for example, the note of a musical instrument, of a 

 violin or flute, the sounds of the human voice, &c. 



When we hear a note struck, we are able to distinguish 

 three points about it* 



I St — Its " Strength" or " Loudness," which depends on the 

 size of the waves of vibrating air. 



2nd — Its " Height" or " Pitch." This is dependent on the 

 number of vibrations performed in a given time. The 

 greater the number of vibrations the higher or sharper the 

 the note, and, of course, vice versa, the smaller the number, 

 the graver, or more bass will be the sound ; practically 32 

 vibrations in one second is the smallest number capable of 

 producing sound, and even then the pitch will be so low as 

 hardly to be perceptible— it is in fact a mere " hum." 



There is a good deal of talk just now of lowering the pitch 

 of the " A" tuning fork, in our English orchestras, and it 

 would, no doubt, be a most sensible thing to do, and an 

 immense boon to our public singers, whose voices are prema- 

 turely worn out by having to sing up to the present high 

 pitch — a pitch which has gradually risen in England until it 

 is now nearly half a tone higher than it was in the time of 

 Handel. The middle A was formerly produced by 417 double 

 vibrations, whereas now the A of the London Philharmonic 

 requires 44.0 vibrations. The French legislature has very 

 wisely enacted that the same note shall not be higher 

 than 424. 



I think I before mentioned that a note is said to be sharper 

 than another when it is produced by a larger, and flatter 

 when it is produced by a smaller number of vibrations in a 

 given time. 



There is a vast difference in the capacity of diff"erent ears 

 to perceive acute sounds. I know a gentleman who can 

 never hear the sharp hissing sound emitted by the field 

 cricket, and which has been calculated to require no less than 

 24,000 distinct vibrations in a second to produce it. But 

 some fine and highly educated ears will detect the faint 

 click emitted by 36,000 double vibrations, or (to jump to the 

 other end of the scale) the slight hum produced by i6, the 

 smallest number capable of producing audible sounds. 



