Influence of wall vibrations on the sound of brass wind instruments

The results of an experimental and theoretical investigation of the influence of wall vibrations on the sound of brass wind instruments are presented. Measurements of the transmission function and input impedance of a trumpet, with the bell both heavily damped and freely vibrating, are shown to be consistent with a theory that assumes that the internal pressure causes an oscillation of the diameter of the pipe enclosing the air column. These effects are shown to be most significant in sections where there are flaring walls, which explains why damping these vibrations in cylindrical pipes normally produces no measurable effects

The limitations on applying classical thin plate theory to thin annular plates clamped on the inner boundary

The experimentally measured resonance frequencies of a thin annular plate with a small ratio of inner to outer radii and clamped on the inner boundary are compared to the predictions of classical thin-plate (CTP) theory and a finite-element (FE) model. The results indicate that, contrary to the conclusions presented in a number of publications, CTP theory does not accurately predict the frequencies of a relatively small number of resonant modes at lower frequencies. It is shown that these inaccuracies are attributable to shear deformations, which are thought to be negligible in thin plates and are neglected in CTP theory. Of particular interest is the failure of CTP theory to accurately predict the resonance frequency of the lowest vibrational mode, which was shifted approximately 30% by shear motion at the inner boundary

S-wave splitting in the offshore South Island, New Zealand : insights into plate-boundary deformation

Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 16 (2015): 2829–2847, doi:10.1002/2015GC005882.Local and regional S-wave splitting in the offshore South Island of the New Zealand plate-boundary zone provides constraints on the spatial and depth extent of the anisotropic structure with an enhanced resolution relative to land-based and SKS studies. The combined analysis of offshore and land measurements using splitting tomography suggests plate-boundary shear dominates in the central and northern South Island. The width of this shear zone in the central South Island is about 200 km, but is complicated by stress-controlled anisotropy at shallow levels. In northern South Island, a broader (>200 km) zone of plate-boundary parallel anisotropy is associated with the transitional faulting between the Alpine fault and Hikurangi subduction and the Hikurangi subduction zone itself. These results suggest S-phases of deep events (∼90 km) in the central South Island are sensitive to plate-boundary derived NE-SW aligned anisotropic media in the upper-lithosphere, supporting a “thin viscous sheet” deformation model.United States National Ocean Bottom Seismograph Instrumentation Pool2016-02-2

Transient motion of a circular plate after an impact

The transient response of a flat circular plate to a sudden impact has been studied experimentally and theoretically. High-speed electronic speckle pattern interferometry reveals the presence of pulses that travel around the edge of the plate ahead of the bending motion initiated by the strike. It is found that the transient motion of the plate is well described by Kirchhoff thin-plate theory over a time approximately equal to the time required for the initial impulse to circumvent the plate; however, a more sophisticated model is required to describe the motion after this time has elapsed

Upper mantle seismic anisotropy at a strike-slip boundary: South Island, New Zealand

New shear wave splitting measurements made from stations onshore and offshore the South Island of New Zealand show a zone of anisotropy 100–200 km wide. Measurements in central South Island and up to approximately 100 km offshore from the west coast yield orientations of the fast quasi-shear wave nearly parallel to relative plate motion, with increased obliquity to this orientation observed farther from shore. On the eastern side of the island, fast orientations rotate counterclockwise to become nearly perpendicular to the orientation of relative plate motion approximately 200 km off the east coast. Uniform delay times between the fast and slow quasi-shear waves of nearly 2.0 s onshore continue to stations approximately 100 km off the west coast, after which they decrease to ~1 s at 200 km. Stations more than ~300 km from the west coast show little to no splitting. East coast stations have delay times around 1 s. Simple strain fields calculated from a thin viscous sheet model (representing distributed lithospheric deformation) with strain rates decreasing exponentially to both the northwest and southeast with e-folding dimensions of 25–35 km (approximately 75% of the deformation within a zone 100–140 km wide) match orientations and amounts of observed splitting. A model of deformation localized in the lithosphere and then spreading out in the asthenosphere also yields predictions consistent with observed splitting if, at depths of 100–130 km below the lithosphere, typical grain sizes are ~ 6–7 mm.New Zealand. Ministry of Research, Science, and TechnologyNational Science Foundation (U.S.). Continental Dynamics Program (Grant EAR-0409564)National Science Foundation (U.S.). Continental Dynamics Program (Grant EAR-0409609)National Science Foundation (U.S.). Continental Dynamics Program (Grant EAR-0409835

Four Brothers and a Waka: Investigating Lithospheric Accommodation of Shear and Convergence Underlying the South Island of New Zealand

New seismic anisotropy and P- and S-wave mantle tomography models produced from passive source seismic data provide insight into how mantle lithosphere deforms due to lateral shear and oblique convergence across the South Island of New Zealand. The shear wave splitting measurements show a zone of mantle seismic anisotropy 100 - 200 km wide with orientations of the fast quasi-shear wave nearly parallel to relative plate motion between the Pacific and Australian plates. Anisotropy of increased obliquity to relative plate motion bookend this 100 - 200 km wide zone. A model representing distributed lithospheric deformation matches the observed orientation and amounts of shear wave splitting. Likewise, given certain conditions of grain size in the asthenosphere, localized lithospheric deformation with diffuse shear in the asthenosphere also matches the shear wave splitting measurements. P- and S-wave tomograms show high-speed structure under the northwestern South Island reaching 400 - 450 km deep. This is evidence for oblique westward subduction of Pacific lithosphere since 45 Ma, consistent with estimates from finite rotations of 850 - 1000 km of subduction thought to have occurred since this time. The high-speed zone reaches 200 - 300 km below the depths of the deepest intermediate depth earthquakes, suggesting that ~ 200 - 300 km of slab below them is required to produce sufficient weight to induce the intermediate depth seismicity. Low seismic speeds seen to 200 km along the east coast of the South Island coincide with regions of volcanism and thinned lithosphere. In the central South Island directly under regions of mountain building, high speeds are found to about 200 km deep. This suggests the lack of an unstable drip due to convergence across the South Island, though is consistent with accommodation of convergence via either lithospheric thickening or intracontinental subduction