MEASUREMENT OF THE EFFECT ON VIOLINS OF AGEING AND PLAYING
This is a report on the first three years of a long-term experiment designed to measure how two very similar violins change with time. After being constructed ‘in parallel,’ one is stored under controlled conditions in a museum and is played infrequently, while the other is played regularly by a professional musician. Vibro-acoustic measurements were performed on the instruments and parts thereof during and after construction. Playing and listening tests by a panel of experienced violinists were conducted at completion, after three years with no adjustment, and then after minor adjustments were made to the played violin only. Panels of players and listeners rated the two violins at all stages, and all results are consistent with the null hypothesis: at present there is no significant preference for either instrument over a range of categories.
Vocal tract resonances and the sound of the Australian didjeridu (yidaki). III. Determinants of playing quality.
Traditional didjeridus have a broad range of bore geometries with many details not immediately apparent to a player, and are therefore suitable for examining the relationship between perceived quality and physical properties. Seven experienced players assessed the overall playing quality of 38 didjeridus that spanned a wide range of quality, pitch, and geometry, as well as 11 plastic cylindrical pipes. The ranking of these instruments was correlated with detailed measurements of their acoustic input impedance spectra. Most significantly, the ranked quality of a didjeridu was found to be negatively correlated with the magnitude of its acoustic input impedance, particularly in the frequency range from 1 to 2 kHz. This is in accord with the fact that maxima in the impedance of the player's vocal tract can inhibit acoustic flow, and consequently sound production, once the magnitude of these impedance maxima becomes comparable with or greater than those of the instrument. This produces the varying spectral peaks or formants in the sound envelope that characterize this instrument. Thus an instrument with low impedance and relatively weak impedance maxima in this frequency range would allow players greater control of the formants in the output sound and thus lead to a higher perceived playing quality.
Resonances of a Violin Body Studied by Hologram Interferometry and Acoustical Methods
Hologram interferometry is applied to study resonances of a violin body. A violin is made and after each major step, modes of vibration are studied. The top plate is studied in six steps: without and with f-holes, with f-holes and bass bar, with an artificial sound post, in the assembled instrument without and with strings. The back plate is studied in four steps: without and with artificial sound post, in the assembled instrument without and with strings. Interferograms of the lowest five to seven modes ranging from about 400 to 1 300 Hz are shown. The top plate is shown to be divided into plate and body resonances. The back plate is acting more as a unit together with the ribs thus mainly giving body-resonances. Deformations of the violin are studied when strings are pressed against the fingerboard, by double exposure hologram interferometry. The lowest air resonance of the sounding box and frequency responses are acoustically measured. In playing the unvarnished violin the tone is found powerful and even.