Biomedical subjects

George Bissinger

Publications and source records attributed to George Bissinger.

3 recordsLinked to original sources

PubMed2006

The violin bridge as filter.

The violin bridge filter role was investigated using modal and acoustic measurements on 12 quality-rated violins combined with systematic bridge rocking frequency f(rock) and wing mass decrements deltam on four bridges for two other violins. No isolated bridge resonances were observed; bridge motions were complex (including a "squat" mode near 0.8 kHz) except for low frequency rigid body pivot motions, all more or less resembling rocking motion at higher frequencies. A conspicuous broad peak near 2.3 kHz in bridge driving point mobility (labeled BH) was seen for good and bad violins. Similar structure was seen in averaged bridge, bridge feet, corpus mobilities and averaged radiativity. No correlation between violin quality and BH driving point, averaged corpus mobility magnitude, or radiativity was found. Increasing averaged-over-f(rock) deltam(g) from 0 to 0.12 generally increased radiativity across the spectrum. Decreasing averaged-over-deltam f(rock) from 3.6 to 2.6 kHz produced consistent decreases in radiativity between 3 and 4.2 kHz, but only few-percent decreases in BH frequency. The lowest f(rock) values were accompanied by significantly reduced radiation from the Helmholtz A0 mode near 280 Hz; this, combined with reduced high frequency output, created overall radiativity profiles quite similar to "bad" violins among the quality-rated violins.

Acoustics↗

PubMed2003

Wall compliance and violin cavity modes.

Violin corpus wall compliance, which has a substantial effect on cavity mode frequencies, was added to Shaw's two-degree-of-freedom (2DOF) network model for A0 ("main air") and A1 (lowest length mode included in "main wood") cavity modes. The 2DOF model predicts a V(-0.25) volume dependence for A0 for rigid violin-shaped cavities, to which a semiempirical compliance correction term, V(-x(c)) (optimization parameter x(c)) consistent with cavity acoustical compliance and violin-based scaling was added. Optimizing x(c) over A0 and A1 frequencies measured for a Hutchins-Schelleng violin octet yielded x(c) approximately 0.08. This markedly improved A0 and A1 frequency predictions to within approximately +/- 10% of experiment over a range of about 4.5:1 in length, 10:1 in f-hole area, 3:1 in top plate thickness, and 128:1 in volume. Compliance is a plausible explanation for A1 falling close to the "main wood" resonance, not increasingly higher for the larger instruments, which were scaled successively shorter compared to the violin for ergonomic and practical reasons. Similarly incorporating compliance for A2 and A4 (lowest lower-/upper-bout modes, respectively) improves frequency predictions within +/-20% over the octet.

Journal Article↗

PubMed2003

Modal analysis of a violin octet.

Experimental modal analysis of a complete Hutchins-Schelleng violin octet, combined with cavity mode analysis and room-averaged acoustic analysis, gives a highly detailed characterization of the dynamics for this historic group of instruments. All the "signature" modes in the open string pitch region--cavity modes A0 ("main air") and A1 (lowest longitudinal), C-bout "rhomboid," the first corpus bending modes B1- and B1+ (comprising the "main wood")--were observed across the octet. A0 was always the lowest dominant radiator, below all corpus modes. A1 contributed significant acoustic output only for larger instruments, but was the dominant contributor for the large bass in the "main wood" region. Acoustic results indicate either B1- or B1+ can be the major radiator. Damping results indicate that B1 modes overall radiate approximately 28% of their vibrational energy. "Doublet" B1 modes from substructure couplings were observed for three instruments. "A0-B0" coupling was not significant for the largest instruments. The original flat-plate-based scaling of the "main wood" resonance was generally successful across the octet, although that for the "main air" was not.

Equipment Design↗