scholarly journals SPH Simulation of Acoustic Waves: Effects of Frequency, Sound Pressure, and Particle Spacing

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Y. O. Zhang ◽  
T. Zhang ◽  
H. Ouyang ◽  
T. Y. Li
Keyword(s):  
Acoustic Waves ◽  
Sound Pressure ◽  
Sound Propagation ◽  
Limited Range ◽  
Sound Frequency ◽  
Numerical Error ◽  
Logarithmic Scale ◽  
Pressure Amplitude ◽  
Sph Method ◽  
Particle Spacing

Acoustic problems consisting of multiphase systems or with deformable boundaries are difficult to describe using mesh-based methods, while the meshfree, Lagrangian smoothed particle hydrodynamics (SPH) method can handle such complicated problems. In this paper, after solving linearized acoustic equations with the standard SPH theory, the feasibility of the SPH method in simulating sound propagation in the time domain is validated. The effects of sound frequency, maximum sound pressure amplitude, and particle spacing on numerical error and time cost are then subsequently discussed based on the sound propagation simulation. The discussion based on a limited range of frequency and sound pressure demonstrates that the rising of sound frequency increases simulation error, and the increase is nonlinear, whereas the rising sound pressure has limited effects on the error. In addition, decreasing the particle spacing reduces the numerical error, while simultaneously increasing the CPU time. The trend of both changes is close to linear on a logarithmic scale.

scholarly journals The Effect of Frequency Acoustic Stimulation Sound on Intrauterine Weakening of Pregnant Sheep

2017 ◽  
Vol 3 (6) ◽  
pp. 125
Author(s):  
Djamil Suherman ◽  
Hermanto Tri Joewono ◽  
I Komang Wiarsa Sardjana
Keyword(s):  
Abdominal Wall ◽  
Sound Pressure ◽  
Acoustic Stimulation ◽  
Uterine Wall ◽  
Sound Frequency ◽  
Pregnant Sheep ◽  
Post Test ◽  
The Difference ◽  
Level Of Sound Pressure ◽  
Veterinary Faculty

Research to determine changes in intrauterine sound pressure in pregnant sheep after administration acoustic stimulation outside of the abdominal wall at some frequency sounds. The study was conducted at the Animal Hospital of Veterinary Faculty of Airlangga University. Pre test experimental design with pre- and post-test one group to assess intra-uterine sound pressure changes. The study was conducted at two lambs pregnant aterm after acoustic stimulation at a distance of 10 cm from the surface of the abdominal wall to the sound pressure 80,85,90,95 and 100 decibels and sound frequency of 31.5, 63, 125, 250, 500, 1000, 2000, 4000, 6000 and 8000 hertz. The results showed that the difference between the sound pressure outside of the abdominal wall with intrauterine sound pressure on both the pregnant sheep by an average of 16.7570 ± 8.0797 decibels. This shows their weakening sound after passing through the abdominal wall and the uterine wall. By using a paired t-test, this weakening statistically significant. At frequencies from 31.5 to 1000 hertz weakening values from 5.2 to 17.1 decibels while in 2000-8000 hertz frequency weakening value of 20.2 to 30.8 decibels. The conclusion that the stimulation of noise from outside the walls of the abdomen weakening sound after penetrating the abdominal wall and the uterine wall. Weakening occur at every level of sound pressure and at every level of a given frequency. Weakening value becomes greater at frequencies above 1000 hertz.                                                                                                       Keywords: weakening, sound pressure, sound frequency, pregnant sheep.

scholarly journals Capturing the dynamics of peripersonal space by integrating sound propagation properties and expectancy effects

2019 ◽  
Author(s):  
Lise Hobeika ◽  
Marine Taffou ◽  
Thibaut Carpentier ◽  
Olivier Warusfel ◽  
Isabelle Viaud-Delmon
Keyword(s):  
Sound Propagation ◽  
Current Method ◽  
Peripersonal Space ◽  
The Body ◽  
Logarithmic Scale ◽  
List Type ◽  
Expectancy Effects ◽  
Near Space ◽  
Propagation Properties ◽  
Tactile Integration

AbstractHighlightsLogarithmically distributed auditory distances provides an apt granularity of PPSMeasuring expectation helps to interpret behavioral impact of audiotactile integrationTactile RTs follows a logarithmic decrease due to audiotactile integrationPeripersonal space is better characterized and quantified with this refinementBackgroundHumans perceive near space and far space differently. Peripersonal space, i.e. the space directly surrounding the body, is often studied using paradigms based on auditory-tactile integration. In these paradigms, reaction time to a tactile stimulus is measured in the presence of a concurrent auditory looming stimulus.New MethodWe propose here to refine the experimental procedure considering sound propagation properties in order to improve granularity and relevance of auditory-tactile integration measures. We used a logarithmic distribution of distances for this purpose. We also want to disentangle behavioral contributions of the targeted audiotactile integration mechanisms from expectancy effects. To this aim, we added to the protocol a baseline with a fixed sound distance.ResultsExpectation contributed significantly to overall behavioral responses. Subtracting it isolated the audiotactile effect due to the stimulus proximity. This revealed that audiotactile integration effects have to be tested on a logarithmic scale of distances, and that they follow a linear variation on this scale.Comparison with Existing Method(s)The granularity of the current method is more relevant, providing higher spatial resolution in the vicinity of the body. Furthermore, most of the existing methods propose a sigmoid fitting, which rests on the intuitive framework that PPS is an in-or-out zone. Our results suggest that behavioral effects follow a logarithmic decrease, thus a response graduated in space.ConclusionsThe proposed protocol design and method of analysis contribute to refine the experimental investigation of the factors influencing and modifying multisensory integration phenomena in the space surrounding the body.

COMPARISON OF THE EFFECTS OF MEDIUM MOTION AND ITS INHOMOGENEITY ON SOUND PROPAGATION IN THE OCEAN

1996 ◽  
Vol 04 (04) ◽  
pp. 385-397
Author(s):  
NATALIE S. GRIGORIEVA
Keyword(s):  
Sound Wave ◽  
Gulf Stream ◽  
Sound Pressure ◽  
Adiabatic Approximation ◽  
Sound Propagation ◽  
Medium Density ◽  
Normal Waves ◽  
Linear Partial Differential Equations ◽  
Oscillation Velocity ◽  
Moving Fluid

The purpose of this paper is to compare the effects of medium motion and its inhomogeneity on sound propagation in the ocean at frequencies from a few tens to a hundred Hz for the sound paths up to several hundreds kilometers in length. It is considered the acoustic propagation passing through a cyclonic eddy and the Gulf Stream current. In moving fluid, the sound propagation is described by a system of seven linear partial differential equations for seven unknown elements of a sound wave. These are the sound pressure, the particle oscillation velocity in a sound wave as well as the changes in medium density, its entropy and concentration of the salt caused by the passage of a sound wave. All these elements of a sound wave are seek in the form of a sum of the quasi-normal waves using the modification of the method of horizontal rays/vertical modes. The numerical simulations are carried out on the base of formulas taking into account the first correction to the adiabatic approximation.

Rectification of Acoustic Waves

1974 ◽  
Vol 52 (17) ◽  
pp. 1726-1730 ◽  
Author(s):  
S. S. Mathur ◽  
M. S. Sagoo
Keyword(s):  
Energy Density ◽  
Acoustic Wave ◽  
Acoustic Waves ◽  
Ultrasonic Waves ◽  
Pressure Amplitude ◽  
The Difference

The difference in the behavior of the denser and the rarer regions of a longitudinal travelling acoustic wave is utilized to produce the phenomenon of rectification of ultrasonic waves. It has been shown that, under appropriate conditions, the energy density of sound in the regions of rarefaction can be increased while in the regions of compression the energy density is decreased. It is found that under suitable conditions, the pressure amplitude in the rarer regions is about 4% larger than that in the denser regions. The measurement of this difference in amplitude can be used to determine the parameter of nonlinearity.

Spectrum Analysis of Infrasound Signal

2014 ◽  
Vol 644-650 ◽  
pp. 4334-4337
Author(s):  
Bin Wang
Keyword(s):  
Frequency Spectrum ◽  
Frequency Distribution ◽  
Spectrum Analysis ◽  
Sound Pressure ◽  
Power Level ◽  
Amplitude Spectrum ◽  
Frequency Component ◽  
Pressure Amplitude ◽  
Frequency Spectrum Analysis ◽  
Infrasound Signal

In this paper, frequency spectrum of infrasound signal collected was analyzed based on MATLAB. The infrasound power level of change with frequency distribution and the infrasound harmonic of each frequency component of the sound pressure amplitude can be made up judgment visually by frequency spectrum analysis and amplitude spectrum analysis, and thus we can obtain different conditions of infrasound properties scientifically and quantitatively.

Behaviour of an air-assisted jet submitted to a transverse high-frequency acoustic field

2009 ◽  
Vol 640 ◽  
pp. 305-342 ◽  
Author(s):  
F. BAILLOT ◽  
J.-B. BLAISOT ◽  
G. BOISDRON ◽  
C. DUMOUCHEL
Keyword(s):  
Heat Release ◽  
Acoustic Field ◽  
Acoustic Waves ◽  
High Frequency ◽  
Gas Flow ◽  
Liquid Core ◽  
Liquid Jet ◽  
Pressure Amplitude ◽  
Instantaneous Rate ◽  
Rate Of Heat Release

Acoustic instabilities with frequencies roughly higher than 1 kHz remain among the most harmful instabilities, able to drastically affect the operation of engines and even leading to the destruction of the combustion chamber. By coupling with resonant transverse modes of the chamber, these pressure fluctuations can lead to a large increase of heat transfer fluctuations, as soon as fluctuations are in phase. To control engine stability, the mechanisms leading to the modulation of the local instantaneous rate of heat release must be understood. The commonly developed global approaches cannot identify the dominant mechanism(s) through which the acoustic oscillation modulates the local instantaneous rate of heat release. Local approaches are being developed based on processes that could be affected by acoustic perturbations. Liquid atomization is one of these processes. In the present paper, the effect of transverse acoustic perturbations on a coaxial air-assisted jet is studied experimentally. Here, five breakup regimes have been identified according to the flow conditions, in the absence of acoustics. The liquid jet is placed either at a pressure anti-node or at a velocity anti-node of an acoustic field. Acoustic levels up to 165 dB are produced. At a pressure anti-node, breakup of the liquid jet is affected by acoustics only if it is assisted by the coaxial gas flow. Effects on the liquid core are mainly due to the unsteady modulation of the annular gas flow induced by the acoustic waves when the mean dynamic pressure of the gas flow is lower than the acoustic pressure amplitude. At a velocity anti-node, local nonlinear radiation pressure effects lead to the flattening of the jet into a liquid sheet. A new criterion, based on an acoustic radiation Bond number, is proposed to predict jet flattening. Once the sheet is formed, it is rapidly atomized by three main phenomena: intrinsic sheet instabilities, Faraday instability and membrane breakup. Globally, this process promotes atomization. The spray is also spatially organized under these conditions: large liquid clusters and droplets with a low ejection velocity can be brought back to the velocity anti-node plane, under the action of the resulting radiation force. These results suggest that in rocket engines, because of the large number of injectors, a spatial redistribution of the spray could occur and lead to inhomogeneous combustion producing high-frequency combustion instabilities.

scholarly journals Prediction and Reduction of Aerodynamic Noise of the Multiblade Centrifugal Fan

2014 ◽  
Vol 6 ◽  
pp. 712421 ◽  
Author(s):  
Shuiqing Zhou ◽  
Jun Wang
Keyword(s):  
Flow Field ◽  
Sound Pressure ◽  
Acoustic Analysis ◽  
Low Noise ◽  
Aerodynamic Noise ◽  
Hybrid Technique ◽  
Field Calculation ◽  
Pressure Amplitude ◽  
Centrifugal Fan ◽  
Hybrid Techniques

An aerodynamic and aeroacoustic investigation of the multiblade centrifugal fan is proposed in this paper, and a hybrid technique of combining flow field calculation and acoustic analysis is applied to solve the aeroacoustic problem of multiblade centrifugal fan. The unsteady flow field of the multiblade centrifugal fan is predicted by solving the incompressible Reynolds-averaged Navier-Stokes (RANS) equations with conventional computing techniques for fluid dynamics. The principal noise source induced is extracted from the calculation of the flow field by using acoustic principles, and the modeled sources on inner and outer surfaces of the volute are calculated with multiregional boundary element method (BEM). Through qualitative analysis, the sound pressure amplitude distribution of the multiblade centrifugal fan in near field is given and the sound pressure level (SPL) spectrum diagram of monitoring points in far field is obtained. Based on the analysis results, the volute tongue structure is adjusted and then a low-noise design for the centrifugal fan is proposed. The comparison of noise tests shows the noise reduction of improved fan model is more obvious, which is in good agreement with the prediction using the hybrid techniques.

Multi-Modal Acoustic Flow Decomposition Examined in a Hard Walled Cylindrical Duct

2015 ◽  
Vol 39 (2) ◽  
pp. 289-296 ◽  
Author(s):  
Stefan Weyna ◽  
Witold Mickiewicz
Keyword(s):  
Acoustic Waves ◽  
Sound Propagation ◽  
Practical Interest ◽  
Sound Intensity ◽  
Wide Band ◽  
Acoustic Energy ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Circular Duct ◽  
Duct Geometry

Abstract Flow fields could be of great interest in the study of sound propagation in aeroengines. For ducts with rigid boundaries, the fluid-resonant category may contribute significantly to unwanted noise. An understanding of the multi-modal propagation of acoustic waves in ducts is of practical interest for use in the control of noise in, for example, aero-engines, automotive exhaust and heating or ventilation systems. The purpose of our experiments was to test the acoustic energy transmission of duct modes based on studies carried out by the sound intensity technique. Sound intensity patterns in circular duct are discussed of modal energy analysis with particular reference to proper orthogonal decomposition and dynamic mode decomposition. The authors try to justify some advantages of the sound intensity experimental research in this area. In the paper, the wide-band sound signal propagated from source approximated with loudspeaker in hard-walled duct is imaged using a sound intensity - based approach. For a simple duct geometry, the sound intensity field is examined visually and by performing a modal decomposition greater insight into the acoustic structures is obtained. The image of sound intensity fields below and above “cut-off” frequency region are found to compare acoustic modes which might resonate in duct.

Self-generation of organized waves in an impinging turbulent jet at low Mach number

1982 ◽  
Vol 117 ◽  
pp. 425-441 ◽  
Author(s):  
Donald Rockwell ◽  
Andreas Schachenmann
Keyword(s):  
Mach Number ◽  
Phase Difference ◽  
Acoustic Waves ◽  
Near Field ◽  
Turbulent Jet ◽  
Maximum Pressure ◽  
Pressure Amplitude ◽  
Axisymmetric Cavity ◽  
Low Mach Number ◽  
Oscillation Frequencies

Self-generation of highly organized waves in a nominally turbulent jet at very low Mach number can arise from its impingement upon the downstream orifice of an axisymmetric cavity, having an impingement length much shorter than the corresponding acoustic wavelength. The oscillation frequencies are compatible with the resonant modes of a long pipe located upstream of the cavity and with jet-instability frequencies based on the column mode (0·3 [siml ] SD [siml ] 0·6), as well as the near-field shear layer mode (0·016 [siml ] Sθ0 [siml ] 0·03). Moreover, the frequency of the organized wave is constant from separation to impingement; consequently vortex pairing does not occur.Within the cavity, the pressure amplitude associated with the organized wave is directly related to the phase difference between the organized velocity fluctuations at separation and impingement. Maximum pressure amplitude occurs when this phase difference, measured along the cavity (i.e. jet) centre-line, is 2nπ. Streamwise amplitude and phase distributions of the organized wave cannot be explained from purely hydrodynamic considerations; however, they can be effectively modelled by superposing contributions from hydrodynamic and acoustic waves. This aspect has important consequences for externally excited jets as well.

scholarly journals Coal-Rock Recognition in Top Coal Caving Using Bimodal Deep Learning and Hilbert-Huang Transform

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Guoxin Zhang ◽  
Zengcai Wang ◽  
Lei Zhao ◽  
Yazhou Qi ◽  
Jinshan Wang
Keyword(s):  
Deep Learning ◽  
Transfer Learning ◽  
Acoustic Waves ◽  
Sound Pressure ◽  
Mechanical Vibration ◽  
Training Sample ◽  
Fine Tuning ◽  
Learning Method ◽  
Hilbert Huang Transform ◽  
Coal Rock

This study employs the mechanical vibration and acoustic waves of a hydraulic support tail beam for an accurate and fast coal-rock recognition. The study proposes a diagnosis method based on bimodal deep learning and Hilbert-Huang transform. The bimodal deep neural networks (DNN) adopt bimodal learning and transfer learning. The bimodal learning method attempts to learn joint representation by considering acceleration and sound pressure modalities, which both contribute to coal-rock recognition. The transfer learning method solves the problem regarding DNN, in which a large number of labeled training samples are necessary to optimize the parameters while the labeled training sample is limited. A suitable installation location for sensors is determined in recognizing coal-rock. The extraction features of acceleration and sound pressure signals are combined and effective combination features are selected. Bimodal DNN consists of two deep belief networks (DBN), each DBN model is trained with related samples, and the parameters of the pretrained DBNs are transferred to the final recognition model. Then the parameters of the proposed model are continuously optimized by pretraining and fine-tuning. Finally, the comparison of experimental results demonstrates the superiority of the proposed method in terms of recognition accuracy.

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