Diseases of the chest and the principles of physical diagnosis . te 54 ACOUSTICS IN PHYSICAL DIAGNOSIS 55 On different, though accurately attuned instruments—^flute, violin,clarionet—the same fundamental note may be sounded, yet the indi-viduality of each instrument remains distinct; we can distinguish one fromthe other. Now this individual difference—timbre, klang, quality—isdependent upon the character of the overtones. The individual qualityof different voices is dependent upon similar factors. Unrhythmic Vibrations.—Theoretically if a string could be struck ata minute point, by a hard hamm
Diseases of the chest and the principles of physical diagnosis . te 54 ACOUSTICS IN PHYSICAL DIAGNOSIS 55 On different, though accurately attuned instruments—^flute, violin,clarionet—the same fundamental note may be sounded, yet the indi-viduality of each instrument remains distinct; we can distinguish one fromthe other. Now this individual difference—timbre, klang, quality—isdependent upon the character of the overtones. The individual qualityof different voices is dependent upon similar factors. Unrhythmic Vibrations.—Theoretically if a string could be struck ata minute point, by a hard hammer, in 0 time, the vibrations would tendto remain localized, and those points of the string which had not beendirectly struck would begin to vibrate slowly and unrhythmically. Asa result the overtones and especially the higher overtones—^the unhar-monious ones—would disproportionately increase in strength and anunpleasant metallic note result (Helmholtz). In the case of the pianothis is obviated by having the strings struck by soft broad hammers,. Fig. 54.—Diagrammatic illustrations of a vibrating string. First, as a whole; second, withone nodal point; third, with two nodal points; fourth, with three nodal points. which remain in contact long enough to ensure a continuous vibration ofthe whole string, and are so placed as to dampen the unharmonious over-tones by eliminating their nodal points. If in any sound-producing bodythe elastic equilibrium be briefly and locally disturbed, unrhythmicvibrations result. Very unrhythmic vibrations allow the distant overtonesto preponderate, and a metallic quality is produced. This occurs regard-less as to whether we are practicing auscultation or percussion, and regard-less as to whether these higher overtones are heard together with thefundamental (amphoric breathing) or separately. All the metallicsound phenomena, of auscultation and percussion are thus produced(metallic ring, bell tympany, amphoric breathing, cracked-pot
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