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, <br /> k <br /> N <br /> Ii.' <br /> I <br /> ,., <br /> ii Pure tones I <br /> , <br /> I 410 <br /> In acoustics , a tone is a sound that gives a definitelsensation of <br /> pitch , loudness , and timbre . A pure tone is a sound wave characterized <br /> I <br /> by singleness of pitch. A tuning fork emits a pure tone . What we refer <br /> to as the "whine" of a turbofan jet engine is usually a combination of <br /> several pure tones . Pure tones can be the most annoying to listeners . <br /> Figure 5 is a graphic representation of the landing noise of a jet <br /> . 1 <br /> aircraft , in which pure tones are identified . <br /> , 1 <br /> 1 <br /> 0100 <br /> Ii ) 1 ' II 11 ii II 11 11111 <br /> 4. <br /> 0 <br /> PURE TONES <br /> , <br /> • 90 _ <br /> 6. . i <br /> cil , <br /> -0 1 <br /> i <br /> ....i 1 <br /> ------ -- 111111 <br /> ›. ! <br /> L1J <br /> . ...I <br /> rac <br /> 67 _NJ__ <br /> D . <br /> cn 1 <br /> cc I <br /> 0 <br /> Z 1 <br /> M 1 <br /> 050 I . J i II it , ii II II _ _11 Ili <br /> 0 63 125 250 500 1000 2000 4000 8000 <br /> 1/3 OCTAVE BAND CENTER FREQUENCY (Hz) <br /> FIG. 5. LANDING NOISE OF A JET PLANE, SHOWING PURE TONES. <br /> 0 <br /> 14 <br /> 1 . . <br /> 1 <br /> 1 1 <br /> ., ... , ... ..._ I <br />