Human articulations are characteristic examples of different forms of noise. The vowels are intermediate between clangs and noises with predominantly clang character; the resonants are noises of long duration, and the proper consonants noises of short duration.

In whispers the vowels become simply noises. The circumstance that the differences in vowels are perfectly distinct in whispers, goes to prove that the character of vowels depends essentially on their noise-elements.

It is [p. 101] probable that simple sensations of noise (p. 49) enter into all noises together with the numerous tonal elements that no to make them up. The irregular air-vibrations arising from the disturbances in the tonal waves, excite both the nervous elements in the vestibule of the labyrinth, which are sensitive to such stimulations, and the auditory nerve fibres themselves.

7a. Helmholtz's resonance hypothesis has aided us materially in understanding the physiological substratum of intensive auditory ideas, especially those of clangs (p. 51). It is assumed that certain parts of the auditory organ are so tuned that tonal waves of a given rate always set in sympathetic vibration only the part,correspondingly tuned. This explains in a general way the analyzing ability of the auditory sense, as a result of which we can distinguish the elements not only in a compound clang, but to some extent even in a single clang. The resonance hypothesis, however, accounts physiologically for only one side of tonal fusion. the persistence of the single sensation in the total intensive idea, not for the other side, the more or less intimate combination of the elements. The assumption of an imaginary "organ of fusion" in the brain for this purpose, is one of those fictions that are more harmful than helpful, in which the attempt is made to satisfy a demand for explanation with an empty word. The tonal elements that produce an intensive clang-idea persist as real sensations and still give up their independence more or less in the total idea. Tonal fusion is, then, a psychical process and requires a psychological explanation. But since this fusion is very different under different objective conditions, as, for example, when the impressions are due to the combined vibrations from a single source or to vibrations from several distinct sources; these differences must have some physiological and physical grounds for their explanation. The most natural way to attempt such an explanation is properly to supplement the resonance hypothesis.

If we assume that besides the analysing parts of the auditory organ, the resonant membrane, still others exist which are effected by the total, unresolved clang, we have a sufficient physiological substratum for the different effects of the various conditions. The [p. 102] observations (p. 41) on birds deprived of their labyrinths make it possible to infer that the auditory nerve-fibres in the canals of the labyrinth may be such organs. Then, too, the existence of beat-tones (p. 99), which sometimes surpass the primary tones in intensity, and the observation that the interruptions of a single tone may unite to form a second sensation when sufficiently rapid, both seem to require a similar supplementation of the resonance hypothesis.

[ 1] The case is different when the fundamental itself contains overtones of noticeable intensity, which are also repeated as independent clangs in the compound tone. The single clangs of such a series arrange themselves in the same phases as these overtones, and the compound clang has the character of a single clang with very strong overtones. Helmholtz concluded from experiments in which he combined in various ways simple clangs from tuning-forks, that differences in phase have no influence on the clang-color. But as the idea of a single clang can not be produced in this way, it is probable that an entirely constant relation of the phases of different tonal vibrations from independent sources can never be brought about with this method. Experiments by R.

Koenig tell for the influence on the clang-color, of the form of the clang as determined by the relation of the vibration-phases