![]() ![]() Sound waves can be reflected, refracted (or bent), and absorbed as light waves can be. Since the ability to conduct sound is dependent on the density of the medium, solids are better conductors than liquids, liquids are better conductors than gases. Sound travels more slowly in gases than in liquids, and more slowly in liquids than in solids. it is increased to about 1,130 ft per second, or an increase of about 2 ft per second for every centigrade degree rise in temperature. it is approximately 1,089 ft per second, but at 20℃. The velocity of sound is not constant, however, for it varies in different media and in the same medium at different temperatures. For example, if the velocity of sound in air is 1,130 ft per second and the frequency of vibration is 256, then the wave length is approximately 4.4 ft. The wavelength of a sound can be determined by dividing the numerical value for the velocity of sound in the given medium at the given temperature by the frequency of vibration. ![]() The wavelength depends upon the velocity of sound in a given medium at a given temperature and upon the frequency of vibration. The length of a sound wave, or the wavelength, is measured as the distance from one point of greatest condensation to the next following it or from any point on one wave to the corresponding point on the next in a train of waves. This graph, however, is merely a representation and is not an actual picture of a wave. Sound waves with frequencies less than those of audible waves are called subsonic those with frequencies above the audible range are called ultrasonic (see ultrasonics).Ī sound wave is usually represented graphically by a wavy, horizontal line the upper part of the wave (the crest) indicates a condensation and the lower part (the trough) indicates a rarefaction. ![]() Sounds are generally audible to the human ear if their frequency (number of vibrations per second) lies between 20 and 20,000 vibrations per second, but the range varies considerably with the individual. Because such a wave travels by disturbing the particles of a material medium, sound waves cannot travel through a vacuum. Taken together a condensation and a rarefaction make up a sound wave such a wave is called longitudinal, or compressional, because the vibratory motion is forward and backward along the direction that the wave is following. In other words, the vibratory motion set up by the violin string causes alternately in a given space a crowding together of the molecules of air (a condensation) and a thinning out of the molecules (a rarefaction). In the meantime, however, the molecules which were at first crowded together have transmitted some of their energy of motion to other molecules still farther on and are returning to fill again the space originally occupied and now left empty by the retreating violin string. When it moves back again past its original position and on to the other side, it leaves behind it a nearly empty space, i.e., a space with relatively few molecules in it. For example, when a violin string vibrates upon being bowed or plucked, its movement in one direction pushes the molecules of the air before it, crowding them together in its path. ![]() Sound waves are generated by any vibrating body. ![]()
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