1,721,016 research outputs found
Revisiting the Lattice Gas Automata: Applications in Acoustics
No full textLattice Gas Automata (LGA) has emerged as a numerical technique based on the propagation and interaction of particles in a lattice. In the Computational Fluid Dynamics field, the Lattice Gas Automata is considered the precursor of the popular Lattice Boltzmann Method. Recognized for its parallelization capabilities and original mesoscopic formulation, the Lattice Gas Automata simulates the small-scale phenomena, making it applicable to various fluid dynamic problems in the time domain. This method indirectly addresses the Navier-Stokes equations within a weakly compressible limit conducive to acoustic wave propagation. This literature review explores the model's basis and some applications in acoustics. The bibliography is collected and presented, identifying the key topics of each study. Beyond offering a retrospective of past research, this work provides insight into the evolution of the lattice models and their potential in the acoustical domain
PROPAGATION OF PRESSURE PULSES IN RECTANGULAR ENCLOSURES USING THE LATTICE BOLTZMANN METHOD
No full textA systematic literature review on Lattice Boltzmann Method applied to acoustics
No full textThe Lattice Boltzmann Method (LBM) can be applied to several fluid dynamic problems in the time domain. This numerical method indirectly solves the Navier–Stokes equations in a weakly compressible limit that allows acoustic wave propagation. This work presents a systematic literature review concerning the application of the LBM in acoustics. Applications found in the literature are classified and presented in different categories, including wave theory, boundary conditions, sound absorption materials, aeroacoustics, and musical acoustics. The increasing amount of research in recent years about aeroacoustics is remarkable, thanks to the intrinsically coupled treatment of the acoustical field and the mean flow, the potential of studying different wave phenomena such as diffraction and scattering, the easy way to model complex geometric boundaries in 2D and 3D, and finally thanks to the increasing available computational power. Some examples were included to illustrate the LBM capabilities to simulate sound wave phenomena, including point source modeling, diffraction and interference of sound waves, jet noise, and edge noise. This work will give a retrospective of the research developed in the past and a perspective on how this numerical method might evolve in the acoustical field
Experimental characterization of the steel tongue drum
No full textThe steel tongue drum (also known as hank drum) is a relatively new musical instrument (2007) in the pitched percussion family, generally made from a metal sheet or from the base of a tank. Several tongues are cut on its surface, making the instrument capable of producing different tones depending on the shape of the tongues. The sound produced has interesting features such as a long decay and a rich and colourful harmony that differentiates this instrument from other mallet instruments as chimes, xylophones or marimbas. The main objective of this work is to present an acoustical characterization of this instrument from direct experimental measurements. Using a class-A measurement system composed of two microphones, a multichannel data acquisition system with pc interface and a computer, the sounds produced by each one of the single tongues were recorded and analysed. Spectrograms were obtained covering from the attack to the decay of each note of the drum. This work is a first step towards the physical characterization of this musical instrument and shows the presence of the harmonic interference between the notes that gives to the steel tongue drum its characteristic sound
EXPERIMENTAL CHARACTERISATION AND OPTIMISATION OF 3D PRINTED STACKS FOR THERMOACOUSTIC REFRIGERATION
No full textIn light of the broadening use of refrigeration in the modern industrial era and considering that conventional refrigeration fluids such as HCFCs, CFCs and HFCs are among the major causes of increased global warming, it seems necessary to implement greener and more sustainable refrigeration solutions rather than continuing to use the ordinary refrigeration methods. Literature emphasizes the need to develop simple and inexpensive acoustic refrigerator prototypes, but one major difficulty results in finding robust and reproducible setups. The following study introduces the description of an experimental and inexpensive construction of a thermo-acoustic refrigerator (TAR), aimed to convert acoustic energy into thermal energy to be used as a heat source in a refrigeration cycle. TARs operate with inert non-polluting fluids such as air, present no frictional losses and require less maintenance costs than ordinary refrigerators, and can operate with either standing or traveling acoustic waves. This work focuses on the repeatability of the setup and the robustness of the results obtained, characterizing an innovative material for the stacks production and proposing a process of optimization of the stack itself. The aim of the study is to realize a simple and economic prototype, which is also robust, easily replicable and innovative from the point of view of the choice of materials, production techniques and their optimisation process. The results concerning the gradient of temperature obtained will be analysed in order to validate the success of the experiment in terms of optimization and reproducibility
Review of acoustic hysteresis in flute-like instruments
No full textThe flute-like instruments (flute, recorders, and organ pipes) have been under physical study for more than a century; an interesting phenomenon, founded but rarely studied is the acoustic hysteresis cycle. A review regarding this acoustical effect it's carried out in this article. When the velocity of the air jet (or the pressure) is increased, the system jumps between the first resonance mode of the coupled pipe to the second mode, but if the excitation velocity decreases, the jump backward is not reached at the same threshold value: this kind of memory of the system is associated with a hysteresis loop. From the early experimental measurements, some approximations refer to an imperfect coupled system between the active input and the passive resonator tube, meaning that the input not only stimulates the natural frequencies of the pipe, but a more complex relation of feedback takes place. Recent theoretical models and computational implementations of this kind of system reproduce the phenomena and show how some geometric parameters, like the labium offset, can affect the presence of even harmonics. It has also been found in an experimental way how input parameters like the angle of the input air jet can be related to the phenomenon. Starting from these experiments a model is proposed that points to nonlinear phenomena where the dissipation mechanism plays a fundamental role. Other parameters can affect the modal transition like the wall vibration of the pipes or the mouth coverage in a flute. The complex Coltman impedance spiral of the jet source can be a way to understand the coupled system and the mode variation in this kind of instruments. Other approaches point to stability and harmonicity analysis of the system, but for now this is an open field to research in experimental, theoretical and computational wa
On the acoustic transparency of perforated metal plates facing a porous fibrous material
No full textThin impervious layers, cloths or perforated plates are usually utilized with fibrous absorbing materials in order to avoid small particles, coming from deterioration over time or from flow abrasive effect, becoming dislodged and polluting the environment. These protective facings are to be carefully considered and analyzed, since they can affect the acoustical behavior of the “backing” material. This study addresses this issue through an experimental survey and a theoretical analysis using the Transfer Matrix Method (TMM). Experiments have been performed in the frequency range 160–2,500 Hz, analyzing the different behaviors due to multiple combinations of percentage of open area and air gap between perforated facing and absorbing material. Experimental data have shown a marked effect of the percentage of perforation, at least up to a threshold value of 20%, whereas the air gap slightly affected the acoustic behavior of the covered absorbing material. The TMM was applied to the tested faced absorbing system, and experimental and theoretical results were compared, showing the good accuracy of the model. Several geometrical configurations were then modeled through TMM and the possibility of using this method in order to assess the acoustic transparency of perforated metal plates was assessed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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