Dictionary of Music - Birding America

394 soundboardtra, has a frequency of 440 cycles per second (byinternational agreement); the A exactly an octaveabove this tone has a frequency of 880 cycles persecond. Similar mathematical relationships existbetween other intervals, and it is on the basis ofthese that instruments are tuned (see TEMPERAMENT;also CONCERT PITCH; INTERVAL, def. 2).The intensity, or loudness, of a musical tonedepends on the energy of the vibrations, that is, howhard the tone-producing substance vibrates (or if onethinks of a vibration as a back-and-forth movement,how far backward and forward it moves from a restposition). Physicists call this distance the amplitude.The intensity of a sound gradually lessensfrom the first moment it is produced. A stretchedrubber band makes the loudest sound when it is firstplucked, for it then vibrates with the most energy.The tone then gradually becomes softer (the vibrationsgradually become weaker) until it stops sounding(the vibrations stop completely).The duration of a tone means simply how longit sounds. Some tones sound for only a fraction ofa second, and others for as long as three or fourminutes.The same note played on different instrumentshas a different tone quality. Even though its pitch,intensity, and duration may be the same, it soundsdifferent. The tone quality of instruments, generallycalled tone color or timbre, can be so distinctive thata listener can instantly tell what instrument is beingplayed. The differences in tone color are caused bythe fact that most sounds are made up not of a singlefrequency but of many different frequencies. A violinstring (or enclosed air column) vibrates not onlyalong its whole length, but at the same time alonghalves, thirds, fourths, and many smaller divisionsof its length. Each of these shorter lengths producesa tone of different pitch (and the shorter the length,the higher the pitch). The tone produced by the fulllengthstring is called the fundamental, and it is theloudest of the pitches heard. The tones sounded atthe same time by the shorter portions of the stringare called harmonics or overtones, and each ofthem is related mathematically to the fundamental ina specific way (actually, the divisions of the stringinto two, three, four or more parts correspond to theintervals created by the fundamental and each of theharmonics). Noise, on the other hand, is a mixture offrequencies not related to one another in this way.Another name for the harmonics is partials. Thefundamental is also known as the first partial or theharmonic of lowest frequency, and the overtones areknown as upper partials. (This terminology is confusing,since the second partial is called the firstovertone or first harmonic, the third partial is thesecond overtone or second harmonic, and so on).The fundamental and all the harmonics together areknown as the HARMONIC SERIES.The harmonics have much less intensity (amplitude)than the fundamental and therefore are heardmuch less distinctly. Nevertheless, it is they thataccount for the difference in tone quality among thevarious instruments. Each instrument produces a differentcombination of harmonics with different combinationsof intensities among the harmonics. Thus,although the cello and French horn produce thesame harmonics, they vary in relative loudness(intensity), and as a result the tone of the two instrumentsis very different.The resonance, or fullness, of a musical tonedepends on the presence of another material that ismade to vibrate with the original vibrations and reinforcethem. In the violin the vibrating strings causethe belly to vibrate, reinforcing their tone. In windinstruments like the oboe, the vibrating air columncauses itself to vibrate. Resonance is an importantconsideration for instrument makers; a fine violin,for example, must resonate with all of the fundamentaltones and their harmonics, providing beautifuland consistent tone quality. (See also RES-ONATOR; SOUNDBOARD; SYMPATHETICSTRINGS.)Resonance and tone color are further affected by theplace in which an instrument is heard. The sameinstrument may sound quite different in a smallroom, a large room, and a concert hall, and even inrooms of the same size (see ACOUSTICS).soundboard 1 In stringed instruments, such asthe piano, harpsichord, and zither, a thin board overwhich the strings are strung. When the strings areplayed, the soundboard vibrates sympatheticallywith them, reinforcing their sound. Soundboards aremade of thin strips of wood or some other material,which are glued together and varnished. In worn or