. Elements of acoustical engineering. Electro-acoustics; Sound. 264 MEASUREMENTS equals the pass band of the highly selective tuned amplifier. The high selectivity is usually obtained by means of a quartz filter. The upper side band is passed through the selective tuned amplifier, detected and then measured on a meter. The balance bridge for measuring the total distortion is shown sche- matically in Fig. A part of the output of the oscillator is fed to the apparatus to be tested and another part to the analyzer. The amplitude and phase relations of the fundamentals from the oscillator
. Elements of acoustical engineering. Electro-acoustics; Sound. 264 MEASUREMENTS equals the pass band of the highly selective tuned amplifier. The high selectivity is usually obtained by means of a quartz filter. The upper side band is passed through the selective tuned amplifier, detected and then measured on a meter. The balance bridge for measuring the total distortion is shown sche- matically in Fig. A part of the output of the oscillator is fed to the apparatus to be tested and another part to the analyzer. The amplitude and phase relations of the fundamentals from the oscillator and apparatus to be tested are adjusted by means of suitable networks so that none of. Fig. Schematic arrangement of the apparatus employing a cathode ray tube for indicating the non-Hnear distortion of a loud speaker. the fundamental remains. The remainder is the total harmonic generated by the system under test. This is measured by means of a root-mean- square meter. The above procedure for obtaining the harmonic content requires con- siderable time and sometimes a qualitative indication requiring only a few minutes has been found to be very useful. Figure shows the circuits used in connection with a modern cathode ray oscillograph, having a stabilizing sweep circuit, to indicate qualitatively the extent to which harmonic distortion is introduced by a loud speaker. When the switch is thrown to the right and the sine wave generated in the oscillator is sent into the amplifying system through the attenuator, the cathode ray oscillograph should show a pure sine wave. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Olson, Harry Ferdinand, 1901-. New York, D. Van Nostrand company, inc.
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