SOUND is caused by a disturbance of the atmosphere, which then transmits itself outward through the air. This takes place by having each disturbed air-particle push the one beyond it, so that the disturbance travels outward somewhat like a stroke through a line of billiard balls, or an engine's push through a train of loosely coupled cars.
Sound is either tone or noise, the former being distinguished from the latter by consisting of regular vibrations, where noise is irregular. The push of the air-particles causes hearing by strokes on the eardrum, whereupon certain nerves take the sensation to the brain, which records it as sound. The brain also notes the pitch of the sound, which depends on the number of vibrations (impacts) per second. The human brain can hear such vibrations only between the limits of 16 per second and 38,000 per second, -- from nearly an octave below the piano to over three octaves above it. Vibrations that are below the lower limit come to the ear as separate puffs, if heard at all; while those above the high limit are totally inaudible. The upper limit varies with different people, so that some can, hear tones which others cannot. Certain animals, such as the cat, have a much higher range than mankind.
One may pause here to pay his respects to the question of the supposed relation between color and pitch. Light waves differ wholly from sound waves in being a disturbance of the ether. In sound, the octave above a note has twice as many vibrations as the note itself; and judged by this principle, the visible color-scale, from red to violet, is less than an octave, the violet having more vibrations than the red in about the proportion of 73 to 46. Light waves, too, are incomparably more frequent, and travel much faster, than sound waves. From all this we may draw the conclusion that there is no relation between color and tone. Many musicians have associated the two; but as we may naturally expect,