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Sensations of Tone

stroboscope, Military necessity, phonograph, fundamental law, stethoscope

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>  Three Important Types of Ordinary Sound

The 19th century was primarily a period of experimental development. The first accurate measurements of the speed of sound in water were made in 1826 by French mathematician Jacques Sturm, and throughout the century numerous experiments were made determining the speed of sound of various frequencies in various media with extreme accuracy. The fundamental law that the speed is the same for sounds of different frequencies and depends on the density and elasticity of the medium was determined in these experiments. The stroboscope, the stethoscope, and the siren were all used in the study of sound during the 19th century.

The standardization of pitch occupied much attention in the 19th century. The first suggestion for a standard had been made about 1700 by French physicist Joseph Sauveur, who proposed C equals 256, a convenient standard for mathematical purposes. German physicist Johann Heinrich Scheibler made the first accurate determination of pitch corresponding to frequency and proposed the standard A equals 440 in 1834. In 1859 the French government decreed that the standard should be A equals 435, based on the research of French physicist Jules Antoine Lissajous. This standard was accepted in many parts of the world, including the United States, until well into the 20th century.

During the 19th century the telephone, the microphone, and the phonograph, all of which were useful for further study of sound, were invented. In the 20th century, physicists for the first time had instruments that made possible simple, accurate, quantitative study of sound. By means of electronic oscillators, waves of any type may be produced electronically, then converted into sounds by electromagnetic or piezoelectric means (see Electronics). Conversely, sounds may be converted into electrical currents by means of a microphone, amplified electronically without distortion, and then analyzed by means of a cathode-ray oscilloscope. Modern techniques permit extremely high-fidelity recording and reproduction of sound. See also Phonograph; Sound Recording and Reproduction.

Military necessity in World War I (1914-1918) led to the first use of sound for underwater detection of vessels; sound is now also used for studies of ocean currents and layers, and for sea-bottom mapping (see Sonar). In addition, ultrahigh-frequency (ultrasonic) sound waves are now used in a wide range of technical and medical applications.



Article key phrases:

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