PERCEPTION OF TIMBRE. ANALYSIS OF VOWELS. 903 



such as a ticking watch, is placed horizontally at a distance from the ear, and, 

 by bringing it closer and removing it further away, the most remote point is 

 determined at which the ticking can be heard. The distance is determined by 

 measurement. (2) Itard uses a small hammer, suspended like a pendulum, 

 which strikes on a hard surface when allowed to fall. The sound is increased 

 4-fold, g-fold, and i6-fold when the angle of elevation is 2, 3, or 4 times as great, 

 although this is true only when the elevation does not exceed 60. (3) In a similar 

 manner, balls of different weight may be dropped from different heights on a 

 sounding-plate. In this case the sound-intensities are proportional to the pro- 

 duct of the weight of the ball by the height of the fall. (4) If a tuning-fork is 

 permitted to sound before the ear, always with the same amplitude of vibra- 

 tion, a normal ear hears the note longer than a diseased ear. 



It has been determined with respect to the limits of barely appreciable tone- 

 intensities that a cork sphere, weighing i milligram, falling from a height of i 

 mm. on a glass plate, may be heard at a distance of 5 cm. There are, however, 

 individual variations, and also differences in acuity between the two ears of the 

 same person. Topler and Boltzmann estimate the amplitude of vibration of 

 the air-particles that are capable of setting the tympanic membrane in vibration 

 so that an auditory sensation results as equal to only 0.00004 mm.; Rayleigh 

 estimates it as only o.oooooi mm. Direct observation of movements so minute 

 would exceed the limits of the best microscope, through which it is possible to 

 recognize objects not smaller than 0.000217 mm. in diameter. The author's 

 brother made the discovery that animals make sounds that, on account of their 

 weakness, cannot be heard by human ears. Thus, some Capricorn beetles (Cer- 

 ambyx) produce shrill tones by rubbing a grooved plate on the neck against the 

 sharp edge of the chest. For example, Gracilia pygmacea produces the tone 

 f 111 , with 1413 vibrations, which cannot be heard because of its weakness. 

 [The number of vibrations (s) of the tone is estimated from the length (1) of the 

 rubbing plate of the insect in mm., the number of grooves (a) to each mm., and 

 the time of the rubbing motion; s = (1 . n) : t.] Larger Capricorn beetles produce 

 sounds that can be heard. 



PERCEPTION OF TIMBRE. ANALYSIS OF VOWELS. 



By tone-quality or timbre is meant a special property of tones, by means of 

 which they may be distinguished independently of their pitch and intensity. 

 For example, a flute, a horn, a violin, and a human voice may produce the same 

 note with equal intensity, and yet each is immediately recognized by its quality 

 or timbre. What constitutes the quality? Investigations, especially those 

 of v. Helmholtz, have shown that of all the sound-producing instruments, only 

 the metal rod fastened at one end and swinging to and fro like a pendulum, and 

 the tuning-fork, produce simple oscillatory and continuous vibrations. This 

 may be shown by fastening a fine point to one branch of a tuning-fork, and 

 registering its movements on a moving strip of smoked paper, on which there will 

 appear then perfectly uniform wave-lines, with equal elevations and depressions. 

 Only those sounds that are produced by such simple oscillatory vibrations are 

 called "tones." 



Further investigations have shown that the tones of all musical instruments 

 and of the human voice, all of which have a characteristic quality, are composed 

 of many individual simple tones. Of these, there is one that is especially con- 

 spicuous by reason of its intensity, and which at the same time determines the 

 pitch of the whole composite "tone-picture." This is known as the fundamental 

 tone or keynote. The other, weaker tones, which are added to this fundamental 

 tone or keynote vary in number and intensity for the different instruments. 

 They are called overtones. Their rate of vibration is always 2, 3, 4, or 5 times that 

 of the fundamental tone. In general, it may be said that all those musical tones 

 that possess numerous strong overtones, especially high ones, have a sharp, cut- 

 ting, rough quality (for example trumpet, clarionet), and, on the contrary, tones 

 with few and weak, and especially deep overtones are peculiarly soft and mild 

 (for example flute). Only a trained, musical ear is able, without assistance, to 

 detect the overtones present in a given note, in addition to the fundamental 

 tone. This is easily done, however, with the aid of so-called resonators. These 

 are funnel-shaped hollow receivers connected with the external auditory canal 

 by means of a short tube. They are so attuned that each succeeding resonator 

 possesses as its fundamental tone that of the next following multiple of the first. 



