What Is Sound is being discussed here.Sound is a wave produced by the vibration.Sound is a physical phenomenon that we perceive through our ears. This phenomenon is called a wave.This phenomenon is what is called a wave.When a person opens his mouth and utters speech he is said to emit sound. Anyone in the vicinity with normal ears (or in default thereof a suitable hearing aid) is said to hear the sound. This common experience is a physical phenomenon of the greatest significance to human beings, who may be considered to be immersed in a world of sound having notable influence on most of their everyday activities.
The importance of sounds which come to our attention. Inanimate nature produces the thunder of the storm, the roar and pounding of the surf, the whistling of the wind, the whispering of the trees, the patter of rain, the rippling and gurgling of running water, the humming of wires, the creaking of snow. Even more rich is the vocabulary descriptive of the sounds of living things: the barking and snarling of dogs, mewing of cats, crowing of fowls, roaring of lions, hissing of snakes, the lowing and bellowing of cattle, blatting of goats, chirping of birds and insects, screaming of gulls, crying of infants, etc.
Finally, man, not content with all the racket around him over which he has little or no control, has contrived to produce sounds of almost infinite variety causing both pleasure and pain to countless millions. The boom of cannon, the crack of the pistol, the rattle of musketry and machine-gun fire, the whine of the shell and the blast of its explosion are unpleasantly familiar. The whir of machinery and the ticking of clocks have more agreeable connotations though they might be distracting to some people. But the ace melody and harmony of music are generally admitted to contribute aesthetic enjoyment.
What Is Sound In Physics
The purpose of this article is to give the physicist’s answer to this question; it will be shown that there is far more to sound than “meets the ear” and that the sounds which are not heard are in some respects the most important ones for modem physics and its technical applications.
Sound is a physical phenomenon and the branch of physics which describes it is called acoustics (from the Greek word meaning “hearing”). Physics is an abstract science and its method of description employs mathematical analysis freely. Without such analysis a physicist considers a deep understanding of a physical phenomena unattainable. On the other hand, the general reader understandably prefers to be told the results of scientific description in the language of everyday speech. This article introduces the subject, therefore, with a general non-mathematical survey of sound. This is followed by a more analytical account.
Sound Measurements.
All acoustical phenomena can be studied through the measurement of certain fundamental quantities. These are velocity, frequency, sound pressure or intensity and impedance. To this list might be added the analysis of complex sounds although this really involves the measurement of the previously mentioned quantities performed in a special way. Common methods of measuring these quantities are discussed below.
Velocity.
The velocity of sound in air was the earliest acoustical quantity to be measured. Marin Mersenne is usually credited with making the first estimation (1640) by timing with a pendulum the interval between the uttering of a sound and the return of the echo from a distant reflector. He found the value 316 m. per second; there is no record of the mean temperature. This is an example of what may be called the direct method of velocity measurement, which essentially reduces to the careful measurement of the time it takes a given sound to travel a known distance.
The direct method has also been applied to the measurement of velocity in liquids and solids. In the oath century the. accepted method employs sound signals in the form of pulses produced by electromagnetic or piezoelectric oscillators. In the simplest scheme a radio frequency pulse of. say, 6 me. per second and around 10 microseconds in duration excites a quartz crystal which radiates a corresponding acoustic pulse into the medium which it traverses until it strikes a reflector placed at a given distance from the crystal. In the meantime another pulse is emitted by the crystal. If the first echo coincides with this pulse, the time for the first pulse to travel to the reflector and back equals the time between successively emitted pulses. Since the latter time can be accurately measured (the so-called pulse repetition rate the velocity is readily determined simply as the distance traveled by the pulse divided by the time.
SOUND BARRIER
(It is also called Sonic Barrier) is a sudden increase in the air resistance that occurs when an airplane or other dying object approaches the speed of sound. If the aircraft is not properly designed to fly at supersonic speeds, it might be crippled or destroyed by the strain resulting from the increased resistance. An associated phenomenon is the sonic boom, an explosive sound somewhat like a thunderclap that is caused by a shock wave which forms along the wing surfaces as they surpass the speed of sound; on some larger aircraft under certain conditions a second wave forms at the tail surfaces producing a double wave that is heard by ground observers as two sharp reports.
SOUNDING.
The act of determining the depth of the ocean or any body of water. The number representing the depth of water at any position is “a sounding ’; and a ship is said to be “on soundings” when she is in a portion of the ocean, as over the continental shelves, where bottom is easily reached, and “off soundings” when in deeper water.
