Sound Bar Research Articles

Simulation of mallet percussion instruments by a coupled modal vibroacoustic finite element model.

A three-dimensional coupled vibroacoustic finite element model for physics-based simulations of the sound generation by mallet percussion instruments in the time domain is discussed in the present paper. The mechanical model takes the orthotropic material properties of the wooden sound bars and the nonlinear nature of the interaction force between the mallet head and the sound bar into account while the acoustical model considers radiation into an unbounded domain. A direct coupling of the sound bars, acoustical cavity resonators, and the excitation by a mallet is considered with exploiting the modal basis to reduce the number of degrees of freedom of the system. Both the mechanical and acoustical models are validated by comparing them to measurements performed on an Orff xylophone. A case study shows the capabilities of the coupled model, including the analysis of the energy balance, the effect of tuning the resonator, and the excitation of the torsional modes of the sound bar.

QUALITY IMPROVEMENT OF CAST CYLINDRICAL BAR OF VACUUM INDUCTION MELTING FROM INCONEL 718 ALLOY AT PJSC “RUSPOLIMET”

The analysis of technological processes of smelting and casting of cylindrical bars from Inconel 718 alloy, obtained in a vacuum induction furnace at PJSC “Ruspolimet”, was performed. The existing technology does not ensure the production of a sound bar of the required quality due to the presence of porosity in the axial zone, and also due to liquation at the macro level of elements such as chromium, nickel, niobium. The results have shown the need to adjust the parameters of casting and solidification of bars from the Inconel 718 alloy. The task to get high-quality sound bar was set without changing the main technical parameters of production, namely: type of furnace – vacuum induction furnace with capacity of 3 tons; material of the furnace lining – ceramics based on aluminum oxide Al2O3 ; type of the casting mold – cylindrical mold for bar diameter of410 mm; diameter of crystallizer for vacuum-arc remelting –450 mm. With the use of the Thermo-Calc program (version 2017a), the solidus temperatures for the equilibrium solidification process and for the non-equilibrium process were clarified, which were 1211 °С and 1091 °С, respectively. Based on the results obtained, the casting speed (SCM LP) system corrects casting speed by reducing the diameter of the casting nozzle from 32 to28 mm and casting temperature by reducing it from 1470 to1460 °C. According to the corrected technology, a batch of bars has been smelted. From the bar of the first batch, transverse templates were selected to determine the chemical composition and longitudinal temp lates for metallographic analysis. Metallographic studies have been carried out that suggest a decrease in porosity of axial zone of the bar and a decrease in phase separation at the macro level. Based on the results obtained, the authors proposed to introduce approp riate changes in casting technology. It is shown that computer modeling of metallurgical processes of metal casting and crystallization allows developing a technology of obtaining a high-quality bar already at the first redistribution, while avoiding appearance of products that do not meet customer requirements.

Ultrasonic dreams of aclinical renderings

Editor’s note: Make sure you click on the sound bar below when reading this article When specific intra-active technologies of ultrasound and echography violently rendered real bodies, they wondered about the see-through space-times that were left in the dark. The crystals. They read, listened and gossiped with awkwardness, intensity and urgency. Lively and clumsily smoking … Continue reading Ultrasonic dreams of aclinical renderings →

A spheroid model for the sound radiation of a loudspeaker on a sound bar

The sound radiation of a loudspeaker on a sound bar with a slender shape is analyzed. Measurements and boundary element method (BEM) simulations of a rectangular rigid enclosure with a flat piston turn out to be in close agreement up to the frequency limit imposed by the discretization chosen for the BEM. Looking up for a shorter computation time, we consider an analytic model based on a geometrical approximation of the sound bar by a prolate spheroid. The corresponding spheroidal coordinate system allows for an analytical solution of the sound-radiation problem. The following parameters are adjusted: geometry of the ellipse-based spheroid, size and location of the circular piston, minimum order of the spheroidal wave functions that ensures convergence. In the light of the BEM results, we also predict the frequency validity of the analytic model. In order to improve the control of the acoustical field radiated by a sound bar, we discuss the influence of the enclosure edges on the regularity of the sound field pattern. [Work supported by the ANR-13-CORD-0008 EDISON 3D grant from the French National Agency of Research.]

Diffraction formulation for the sound radiation of a loudspeaker on a rigid convex edged shape enclosure

We present a method for calculating the sound radiation of a loudspeaker on a box-shape enclosure. This method is based on the iterative Asheim-Svensson formulation [Asheim et al. J. Acoust. Soc. Am., 2013]. In this geometrical acoustical model, the radiated sound is given by the addition of the direct sound of a baffled piston and the sound scattered by the edges of the loudspeaker enclosure. The latter are expressed in the form of multiple-order edge diffraction components. This method becomes particularly attractive at high frequencies since the maximum order required to get a correct estimation decreases with frequency. Altogether, the method becomes less costly than the Boundary Element Method (BEM) beyond a given frequency. The convergence of the method can be estimated by considering the distance traveled by the creeping wave on the enclosure instead of considering the successive orders of diffraction by each edge. An iterative formulation follows which is well-suited to slender objects such as a sound bar. Comparisons with measurements and results of a BEM calculation will be presented. [Work supported by the ANR-13-CORD-0008 EDISON 3D grant from the French National Agency of Research.]

DSP implementation of surround speaker virtualizer for sound bar systems

This paper describes one solution for an implementation of the surround speaker virtualization module for a digital signal processor in a sound bar system. The main problem in this system, which consists of a decoder, a renderer and a post-processing module, is complex processing of sound in real-time. In order to achieve real-time execution of these operations and offer customers an affordable product, sound bar system is implemented on an embedded platform. A detailed overview of the system architecture and available resources is given, as the development of modules in an embedded system requires optimal resource usage. Furthermore, numerous challenges and constraints of real-time system programming are presented through the implementation of surround virtualization module, an integral part of the post- processing block. The merits of the proposed architecture are fortified with the measured usage of limited processor resources, and evaluation results confirm that real-time execution of the proposed solution is achieved.

Influence of corrosion on the bond strength of steel rebars in concrete

The problem of the durability of reinforced concrete structures is arisen, dramatically, in the last decades, showing that one of the most dangerous degradation phenomena is connected to the rebars corrosion. When active corrosion grows the oxides occupy a volume of about 2–4 times, with respect to the sound bar, causing a loss of bond, cracking and cover spalling. In this paper the corrosion effects at the steel–concrete interface are analysed. At this aim, pull-out tests are carried out, with different corrosion levels, for the definition of the bond-slip constitutive relationships of the damaged rebars. Furthermore, an analytical model is developed for evaluating the internal pressure due to corrosion products, for concrete specimens without stirrups, in order to provide a procedure for the definition of the maximum bond as a function of the corrosion percentage. Finally the analytical results are validated through a comparison with the experimental outcomes.

Casting of Aluminum Alloy Bar by Semisolid Roll Casting

Rheo-casting of 4045 aluminum alloy bar was operated using an unequal diameter twin roll caster and a cooling slope. The semisolid slurry was made by the cooling slope. The thickness of the bar was 12 mm and width was 100mm. The casting speed was 1m/min. Quantity of the melt poured on the cooling slope was important to make sound bar. The primary crystal became spherical, and its size was about 40μm.

Acoustic correlates of distinctive features of Italian stops

The object of this study was the determination of acoustic correlates of two distinctive features of Italian stops related to voicing and point of articulation. The analysis was carried out on 648 VCV syllables. The correlates found for voicing were the sound bar during the voiced stops occlusion and the low-frequency (LF) burst energy. Informal perceptual tests showed the relevance of only the second correlate. As to the point of articulation, the attention was focused both on formants transition from the first vowel to the following stop and on the spectral shape of the burst. For the formants transition, different groups of templates were obtained for the different vowels. The burst spectrum was then analyzed to obtain a gross representation through four centroids defining three segments with different slopes. Aposteriori classification based on either voicing (sound bar and LF burst energy) or point of articulation (gross spectral shape) yielded on the previous database to a classification score of 88% and 87%, respectively. These strategies were implemented in a system used for the recognition of Italian stops in VCV structures. An inter-linguistic study aimed at comparing Italian dental stops with British English corresponding alveolars in progress.

Sound bar electronic musical instrument

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Method for producing sound bar for percussive musical instruments: sawada, S. and Murase, Y. (Nippon Gakki Seizo Kabushiki Kaisha, Japan) US Pat 4 718 964 (12 January 1988)

Method for producing sound bar for percussive musical instruments: sawada, S. and Murase, Y. (Nippon Gakki Seizo Kabushiki Kaisha, Japan) US Pat 4 718 964 (12 January 1988)

Method for producing sound bar for percussive musical instruments

In construction of a FRP sound bar preferably by lamination for percussive musical instruments, 30 to 80% by volume of reinforcing fibers are oriented in a resin matrix at least in the longitudinal direction of the sound bar and a plurality of longitudinal pores are almost uniformly distributed over the entire cross section of the sound bar, for easy and low cost production with ideal sound extension.

Sound bar for percussive musical instruments and a method for producing same

In construction of a FRP sound bar preferably by lamination for percussive musical instruments, 30 to 80% by volume of reinforcing fibers are oriented in a resin matrix at least in the longitudinal direction of the sound bar and a plurality of longitudinal pores are almost uniformly distributed over the entire cross section of the sound bar, for easy and low cost production with ideal sound extension.

Sound bar type percussive musical instrument

In construction of a sound bar type percussive musical instrument, the center sections of tube holders are firmly coupled to the center sections of the front and rear walls of the base frame in order to block the tube holders against undesirable center flexion due to weight of resonator tubes, thereby assuring uniform gaps for all sound bars and resonator tubes.

Adjustable bottom closure for a resonator on sound bar type percussive musical instruments

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