| Test Data
This page contains data collected by Norman Pickering from three violins. The data is preceded by a description of the experiment from which the data was collected, and an explanation of how the data is presented. The violins are as follows:
Data highlighted in red are those which show the most general summary of the violins performance. These data show that the average output from our violins was measured 5.7% greater from the top and 2.7% greater from the back than the output of the old Italian violin. Also, our violins have approximately the same tonal balance as the old Italian Violin. These tests were conducted in December of 2000. We have since tried to have subsequent tests done on some instruments with newer and better modifications. However, Mr. Pickering has not had his equipment set up since he moved a while ago. VIOLIN TEST RESULTS The instrument is supported by rubber slings at the base of the neck and across the lower bouts just below the corners. It is tuned to pitch and the strings are damped with a felt pad inserted between the strings and the fingerboard. The chinrest is undisturbed. A proprietary electromagnetic transducer, lightly in contact with the center of the bridge, applies a vibrating lateral force analogous to that of a bowed string. The force is essentially constant over the test frequency range. The driving waveform is a sawtooth, and the fundamental frequency is stepped in 45 semitone intervals from G3 (196 Hz) to D7 (2349 Hz). A short interval of steady frequency is followed by two seconds of frequency modulation (vibrato) at 6 Hz with a deviation of plus and minus 50 cents. The complex waveform of the drive contains all harmonics well beyond 8000 Hz, with amplitudes inversely proportional to order number. Data is presented in the form of a table of values and two graphs:
Note: Tonal balance is calculated from the columns F and G above, and is the frequency at the center of the power spectrum. The higher the number, the more acoustic output is shifted toward higher frequencies, and vice versa. 2. A bar chart plotting the data in columns B and C above: The average level for both microphones is shown for each note. All harmonics are present as they would be for a bowed string drive. Unlike the actual string, however, the mechanical drive is at one point on the the bridge (the center) and of constant force at all fundamental frequencies. The data, therefore, eliminates the effect of different strings and shows only the inherent acoustical properties of the instrument. The large difference in loudness from note to note actually exists, and must be compensated for by the player. 3. A graph of the spectrum, as driven by a swept sine wave. The pair of red-line graphs show the spectra at the two microphones with a sine-wave input to the bridge. The upper curve is for the lower microphone and the lower curve is for the upper microphone. These show the actual positions and amplitudes of the principal mechanical and acoustical resonances of an instrument. The normal shape, size and constructional details of a violin dictate the general disposition of these peaks. The exact frequencies and amplitudes are different for every violin and control which harmonics of each note are emphasized or suppressed, thereby determining the power and tone quality of a given instrument.
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