Page 21 - Summer 2008

however, he did not experience green when a blue glass was in front of one eye and a yellow in front of the other. When he was examining binaural integration, the import of Wheatstone’s stereoscopic observations was being absorbed, but his descriptions of binaural combination were over- looked.
Heinrich Dove (1803–1879) had considered the opera-
tion of the two ears in a manner analogous to two eyes, and
described an experiment, similar to that of Wheatstone, in
which different tuning forks were held by the side of each
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He reported that beats were audible under these cir- cumstances. Yet Weber reached the opposite conclusion when he carried out a similar study using pocket-watches ticking at slightly different rates. If they were both placed next to the same ear, then the beats could be heard: “But if I hold one watch next to each ear, while indeed I can perceive that one ticks faster than the other, I cannot perceive this repeated rhythm, and the ticking of the two watches therefore gives quite a different impression from that in the first instance.”33 Weber addressed this problem in the context of differences between sensation and interpretation, and specu- lated that two different auditory sensations could not be per- ceived simultaneously.
ear.
In the same year Seebeck reported experiments on lis-
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on color vision, and had investigated binocular color mixing
tening to different sounds in each ear.
He was an authority
however, his experiences did not accord with those reported by others. He observed a mixture of colors rather than rival- ry between them. Seebeck’s experiments were triggered by Dove’s descriptions of stimulating two eyes and two ears. Seebeck used sirens as well as tuning forks to stimulate the ears, and reported that each sound could be localized to the ear receiving it, and that the two sounds were not combined.
Weber’s speculations on the involvement of attention later evoked the interest of Gustav Theodor Fechner (1801–1887), shown in Fig. 6. Fechner became interested in the combination of sounds presented to different ears. Not only did he find it impossible to hear beats when watches, with slightly different ticking rates, were placed at each ear, but he also described a type of rivalry between the two
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He found the same effects when he used earflaps to surround the watches—a move towards the use of earphones. This provid- ed further evidence for his comparison between hearing with the two ears and seeing with the two eyes. In pursuing this analogy, he questioned the equivalence between presenting different colors to each eye and different sounds to each ear. Fechner repeated the experiments with tuning forks, after the manner of Wheatstone27 and Dove32, and obtained results that were similar to those of Wheatstone, and not to those of Dove. (Fechner also noted that the majority of people have poorer hearing in the right ear than in the left, and indicated
sounds—he heard one and then the other in succession.
Fig. 6. Left– detail of a photogravure of Gustav Theodor Fechner from Kunke.36 Right–“Fechner coloured” by Nicholas Wade. The portrait on the left is also present in the psychometric functions on the right—Fechner can be seen in the area of uncertainty of the curves.
20 Acoustics Today, July 2008