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The sound and underwater sound emitted from a water drop colliding with a water surface are simulated by a new model of the finite difference lattice Boltzmann method. The two-particle immiscible fluid model is modified to simulate sound in the gas phase and underwater simultaneously. In the very early stage after the collision, sounds propagating into the gas and liquid phases are successively detected, and the effects of drop shape and gas bubbles are also observed.

Assessing solution error continues to be a formidable task when numerically solving practical flow problems. Currently, grid refinement is the primary method used for error assessment. The minimum grid spacing requirements to achieve design order accuracy for a structured-grid scheme are determined for several simple examples using truncation error evaluations on a sequence of meshes. For certain methods and classes of problems, obtaining design order may not be sufficient to guarantee low error. Furthermore, some schemes can require much finer meshes to obtain design order than would be needed to reduce the error to acceptable levels. Results are then presented from realistic problems that further demonstrate the challenges associated with using grid refinement studies to assess solution accuracy.

Despite state of the art tracheo-esophageal (TE) voice-rehabilitation after laryn-gectomy, some patients are unable to produce voice of sufficient quality, because of hypotonicity or atonicity of their pharyngo-esophageal (PE) segment. Furthermore, the TE voice is low pitched, which presents a problem especially for female laryngectomized patients. A voice-producing element (VPE) is developed, based on the double-membrane concept, to supply the laryngectomized patients with a better substitute voice. The VPE is comprised of two elastic membranes inside a circular housing that can be inserted in a shunt valve. Four identical prototypes were manufactured and tested in-vitro under physiological conditions. Prototypes were also tested in 17 female laryngectomised patients. An aerodynamic and acoustical analysis was performed, the maximum phonation time, speech rate and intonation capability determined. Finally the voice was perceptual evaluated. Basic sound, containing multiple harmonics, was successfully produced under physiologic air pressure and airflow conditions. The fundamental frequency and sound pressure level could be controlled by changing the driving pressure, thus enabling sufficient intonation. The obtained frequency range (190 - 350 Hz) is appropriate for producing a female voice. The VPE produced a sound with a low noise-to-harmonics ratio (mean 0.15), the efficiency of sound production (5.5-10(-5)) is comparable to normal vocal folds. The clinical study clearly showed that the pitch and sound intensity were increased without an unacceptable increase in driving lung pressure. The flow rates were lower than normal, leading to significantly longer phonation times. Accumulation of mucus did not interfere with speech production. In conclusion, functional restoration of the voice after laryngectomy with a VPE, based on the double-membrane concept, appears a feasible concept for female laryngectomized patients or patients with a hypo- or atonic PE segment.

Background. A sound generator based on a double-membrane design that fits into a regular tracheoesophageal shunt valve may improve voice quality after total laryngectomy in patients rehabilitated with surgical voice prostheses.Methods. Voice-producing element (VPE) prototypes were manufactured using medical grade biocompatible materials and tested in vitro under physiological conditions.Results. Basic sound, containing multiple harmonics, was successfully produced under physiologic air pressure and airflow conditions. The fundamental frequency and sound pressure level (SPL) is controlled by changing the driving pressure, thus enabling sufficient intonation for day-to-day speech. The obtained frequency range (190-350 Hz) is appropriate for producing a female voice. The low noise-to-harmonics ratio (mean 0.15) and also the efficiency of sound production (5.5 X 10(-5) at 80 dB(A) and 0.15 m microphone distance) is comparable to that of normal vocal folds.Conclusions. Functional restoration of the voice after laryngectomy with a double-membrane VPE appears to be a feasible concept for female laryngectomized patients with a hypetonic, or atonic pharyngoesophageal segment. (c) 2007 Wiley Periodicals, Inc.

In a situation where traffic, railway or aircraft noise sources are not present, as it happens in shielded areas, other sources might become relevant in terms of annoyance. This is the case of typical turbomachinery elements, such as fans, compressors or turbines, where sound is generated aerodynamically. As a part of the Sonorus project, where all noise sources in urban environments are considered, the goal of this research is to develop an auralization tool that generates a time domain signal depending on the fan working conditions and the propagation scenario. In this paper, a computational aero-acoustics solver is used to simulate the flow field generated by an axial fan, and the acoustic field is calculated using the Ffowcs-Williams and Hawkings method. The information contained in this acoustic field is used to generate an audio signal for auralization purposes. The model results are evaluated by comparisons with recordings and measurements.