Democratic Sentinel, Volume 16, Number 42, Rensselaer, Jasper County, 4 November 1892 — Oddities of Echoes. [ARTICLE]

Oddities of Echoes.

Did you ever figure on the exact distance that one may be removed from a reflecting surface and yet hear the echo of his voice? It is said that one cannot pronounce distinctly or hear distinctly more than five syllables in a second. This, of course, gives one-fifth of a second for each syllable. Taking 1,120 feet as the velocity ol sound per second, wc have 234 feet as the distance sound will travel in onefifth qf a second. Hence, if a reflecting surface is 112 feet distant, the initial sound of an uttered syllable will be returned to the ear from a distance of 11$ feet, just as the next syllable starts on its journey. In this ease the first fifth of a second is consume 1 in the utterance of a syllable, and the next fifth of a second in hearing its echo. Two syllables would be echoed from a reflecting surface 224 feet distant, three syllables from 338 feet, and so on, within the limits of audibleness. But or the other hand, it is evident that a sharp, quick sound, say that made by a hammer, or a club upon a board, one in which the duration of the sound itself is onetenth of a second or less, would give an echo from half the 112 feet, of fifty-six feet. The above estimates and figures apply to observations made in a temperature of 61 degrees, Fahrenheit, at which scientists tell us that the velocity of. sound is 1,118 feet per second. If the mercury stands at freezing the velocity of sound will only be 1,088 feet per second.— [Philadelphia Press.