Page 20 - Summer 2008

Fig. 5. Left– detail of a portrait of Ernst Heinrich Weber. Right–“Weber colour fractions” by Nicholas Wade. The same portrait of Weber is embedded in a pattern repre- senting psychometric functions. His face is present in both the upper and lower parts of the design, corresponding to the upper and lower thresholds.
he commenced his researches in audition, and was led to the
study of vision through the visual expression of acoustic phe-
nomena. Wheatstone was born in Gloucester and joined the
Wheatstone family business, which was concerned with the
manufacture of musical instruments. He was appointed to
the chair of experimental philosophy at King’s College,
London, at the age of 32, and held the post for the rest of his
22,23
life.
He invented a number of musical instruments, the
most popular of which was the concertina. In the 1820s, he
published work on visual persistence, and constructed a
philosophical toy which traced beautiful patterns—called the
kaleidophone, after Brewster’s kaleidoscope.24 The kaleido-
phone was constructed to amplify the vibrations of rods so
that they could be seen by the naked eye. Silvered glass beads
were attached to the ends of rods having different cross-sec-
tions and shapes; when the rods were bowed or struck com-
plex figures could be seen in the light paths traced by reflec-
tions from the beads. Wheatstone’s early experiments were
addressed to Chladni figures and a range of other acoustic
25
Wheatstone also conducted experiments with tuning forks presented to different ears: “It is well known, that when two consonant sounds are heard together, a third sound results from the coincidences of their vibrations; and that this third
He also invented one of the earliest binaural instruments that he called a microphone as shown in Fig. 4, together with his portrait.
phenomena.
sound, which is called the grave harmonic, is always equal to unity, when the two primitive sounds are represented by the lowest integral numbers. This being premised, select two tun- ing-forks the sounds of which differ by any consonant interval excepting the octave; place the broad sides of their branches, while in vibration, close to one ear, in such a manner that they shall nearly touch at the acoustic axis; the resulting grave har- monic will then be strongly audible, combined with the two other sounds; place afterwards one fork to each ear, and the consonance will be heard much richer in volume, but no audi- ble indications whatever of the third sound will be perceived.” 29
Wheatstone’s description concerning the perceptual fusion of harmonically related tones addressed a related
10
Weber was born in Wittenberg where he studied medicine. Most of his academic life was spent in Leipzig, where he held chairs—first of anatomy and then of physiology. Chladni was a frequent visitor to the Weber household and, with his brother Wilhelm, Weber
31
The observations of both Wells and Wheatstone went unheeded however, and were not cited by the German researchers who addressed similar issues at around that time and in the following decades. One such was Weber (Fig. 5), who is well known as one of the
30
issue to those addressed by Wells.
founders of psychophysics.
He also published two mono- graphs on the senses. In the first, he described binocular color mixing, concluding that the two colors appear as one
wrote a book on wave theory.
Binaural Hearing and the Stethophone 19