Sound

Any thing audible; noise; that which is perceived by the ear. The experiments are numerous by which it has been found, that sound is audible to the distance of 50, 60, or 80 miles; but Dr. Hearne, physician to the king of Sweden, tells us, that at the bombardment of Holmia, in 1658, the sound was heard 30 Swedish miles, which make 180 of ours: and in the fight between England and Holland in 1672, the noise of the guns was heard even in Wales, which cannot be le than 200 miles. The velocity of sound is 380 yards, or 1142 feet in a second of time, as found by very accurate experiment. The exactne of measuring distances by sound, has been sufficiently proved by measuring the same distances by trigonometry. The medium velocity of sound is nearly at the rate of a mile, or 5280 feet in 4²⁄₃ seconds; or a league in 14 seconds; or 13 miles in one minute. But sea miles are to land miles nearly as 7 to 6: therefore sound moves over a sea mile in 5³⁄₄ seconds nearly; or a sea league in 16 seconds. Sound flies 1142 feet in one second. It is a common observation, that persons in good health have about 75 pulsations at the wrist in a minute, consequently in 75 pulsations sound flies about 13 land miles, or 11¹⁄₇ sea miles, which is about 1 land mile in 6 pulsations, and 1 sea mile in 7 pulses, or a league in 20 pulses. The velocity of sound does not very much vary, whether it goes with the wind or against it. As sound moves vastly swifter than the wind, the acceleration it can thereby receive can be but inconsiderable; and the chief effect we can perceive from the wind is, that the sound will be carried to a greater distance by it. Sound will be louder in proportion to the con dens i on of the air. Water is one of the greatest conductors of sound; it can be heard nearly twice as far as on land.