scholarly journals Acoustic radiation patterns of the silo music phenomenon

2021 ◽  
Vol 249 ◽  
pp. 03018
Author(s):  
J.R. Hernández-Juárez ◽  
D.A. Serrano ◽  
A. López-Villa ◽  
A. Medina
Keyword(s):  
Acoustic Waves ◽  
Line Source ◽  
Sound Pressure ◽  
Acoustic Radiation ◽  
Pressure Level ◽  
Discharge Process ◽  
Far Field ◽  
Continuous Line ◽  
Acoustic Source ◽  
Beam Patterns

In this work, we apply the theory of radiation and reception of acoustic waves in the analysis of the acoustic contributions of the silo music phenomenon. The length portion of the silo where the silo music phenomenon occurs is considered a continuous line source. The continuous line source modeled as a simple acoustic source permits the analysis of the acoustic far field, interpreting the polar graphics of the beam patterns of the acoustic contributions. We propose to apply this technique in the silo design to diminish adverse acoustic effects during the discharge process of granular materials. Additionally, we present calculations of the sound pressure level of the silo music phenomenon.

Gyro Rock Crusher and Asphalt Plant Sound Power Levels

2012 ◽  
Author(s):  
Henry A. Scarton ◽  
Kyle R. Wilt
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Low Frequency ◽  
Pressure Level ◽  
Sound Power ◽  
Far Field ◽  
Atmospheric Attenuation ◽  
Frequency Sound ◽  
Sound Pressure Levels ◽  
Rock Crusher

Sound power levels including the distribution into octaves from a large 149 kW (200 horsepower) gyro rock crusher and separate asphalt plant are presented. These NIST-traceable data are needed for estimating sound pressure levels at large distances (such as occurs on adjoining property to a quarry) where atmospheric attenuation may be significant for the higher frequencies. Included are examples of the computed A-weighted sound pressure levels at a distance from the source, including atmospheric attenuation. Substantial low-frequency sound power levels are noted which are greatly reduced in the far-field A-weighted sound pressure level calculations.

A Nonlinear Signal Analysis Scheme for Localization of a Moving Acoustic Source

2009 ◽  
Author(s):  
Nikolaos I. Xiros
Keyword(s):  
Nonlinear Systems ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Linear Time ◽  
Pressure Level ◽  
Coupled Systems ◽  
Data Series ◽  
Source Position ◽  
Acoustic Source ◽  
Analysis Scheme

The synthesis of coupled systems including linear propagation media and nonlinear lumped subsystems is investigated. The resulting coupled system is expected to exhibit improved dynamic behavior. Such improvements are sought after by designing exclusively the lumped nonlinear subsystem and not by modifying the propagation medium. The lumped subsystem can be static or dynamic as well as passive or active. The design method is based on the Volterra-Wiener theory of nonlinear systems combined with the Linear Fractional Transformation employed for the analysis of uncertain linear systems. Although the techniques are applicable to a variety of practical engineering and physical systems, this work addresses acoustic source localization. Indeed, a moving acoustic source can be considered to nonlinearly modify the characteristics of a carrier acoustic wave. Such an acoustic carrier might be a monochromatic or polychromatic tone as well as other broadband signals such as band-limited white or colored noise. The sound source position signal is propagated through a nonlinear operator and then, under noise-free environment assumptions, determines the sound pressure level at the receiver location. In this paper, the proposed method is applied to the simplified case of a one-dimensional acoustic cavity defined by totally reflective barriers. Furthermore, the lossless wave equation is assumed to govern the sound pressure level in the homogeneous domain of interest. However, even in this simple scenario, only the additional assumptions of negligible source velocity and acceleration allow the derivation of an expression for the sound pressure level containing exclusively source displacement. In this context, simulation data series or analytical solutions, approximate or exact, are post-processed in order to determine the Volterra kernels, which effectively are a convenient extension of the impulse response concept in the nonlinear case, of the operator connecting source displacement to sound pressure level at the receiver. The outcome is Linear Time Invariant models depicting the dominant sound propagation dynamics. Then the synthesis stage is based on the properties of interconnected nonlinear systems that are described in the Volterra-Wiener framework. By using such properties, the signal processing algorithm for the estimation of the acoustic source position based on the received sound pressure level is finally developed.

scholarly journals Effects of pipe casing structure on acoustic emission characteristics of underwater pyrotechnic combustion

2019 ◽  
Vol 39 (1) ◽  
pp. 149-157
Author(s):  
Jie Li ◽  
Jun Du ◽  
Xian Chen ◽  
Yanli Wang
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Acoustic Radiation ◽  
Structural Characteristics ◽  
Bubble Formation ◽  
Pressure Level ◽  
Radiation Characteristics ◽  
Acoustic Testing ◽  
Gas Volume ◽  
Broadband Sound

In order to investigate the acoustic radiation characteristics of underwater, a pipe casing was introduced and the effects of its main structural characteristics on underwater combustion acoustic radiation were studied by acoustic testing. The results show that the addition of the pipe casing significantly increased the sound pressure level of underwater pyrotechnic combustion, especially the peak of sound pressure level that was increased by 15.9 dB from 155.5 to 171.4 dB at the frequency of 125 and 100 Hz. But the addition of the pipe casing had little effect on the frequency. These results indicated that adding a pipe casing is effective for improving sound pressure level in underwater pyrotechnic combustion. An increase in nozzle diameter from 10 to 12.5 mm resulted in an increase of gas volume, so the peak of sound pressure level and broadband sound pressure level is higher. Changing the pipe casing direction to vertical downward will make the bubble formation period shorter, which will generate more bubbles and strong wake; the interaction between bubbles and wake results in a higher intensity of turbulence, which accounts for the coalescence and breakup of bubbles in the fluid. Besides, changing the diameter of pipe casing can be used to lower the frequency of underwater noise.

Noise Prediction for Multi-Element Airfoil Based on FW-H Equation

2011 ◽  
Vol 52-54 ◽  
pp. 1388-1393
Author(s):  
Jun Tao ◽  
Gang Sun ◽  
Ying Hu ◽  
Miao Zhang
Keyword(s):  
Flow Field ◽  
Sound Pressure ◽  
Near Field ◽  
Pressure Level ◽  
Aerodynamic Noise ◽  
Noise Prediction ◽  
Far Field ◽  
Acoustic Analogy ◽  
Acoustic Information ◽  
Good Agreement

In this article, four observation points are selected in the flow field when predicting aerodynamic noise of a multi-element airfoil for both a coarser grid and a finer grid. Numerical simulation of N-S equations is employed to obtain near-field acoustic information, then far-field acoustic information is obtained through acoustic analogy theory combined with FW-H equation. Computation indicates: the codes calculate the flow field in good agreement with the experimental data; The finer the grid is, the more stable the calculated sound pressure level (SPL) is and the more regularly d(SPL)/d(St) varies.

Prediction of Far-Field Sound Pressure of a Semisubmerged Cylindrical Shell With Low-Frequency Excitation

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
T. Y. Li ◽  
P. Wang ◽  
X. Zhu ◽  
J. Yang ◽  
W. B. Ye
Keyword(s):  
Cylindrical Shell ◽  
Free Surface ◽  
Sound Pressure ◽  
Acoustic Radiation ◽  
Phase Method ◽  
Far Field ◽  
Radiation Model ◽  
New Approaches ◽  
Modal Coupling ◽  
Field Sound

A sound–structure interaction model is established to study the vibroacoustic characteristics of a semisubmerged cylindrical shell using the wave propagation approach (WPA). The fluid free surface effect is taken into account by satisfying the sound pressure release condition. Then, the far-field sound pressure is predicted with shell's vibration response using the stationary phase method. Modal coupling effect arises due to the presence of the fluid free surface. New approaches are proposed to handle this problem, i.e., diagonal coupling acoustic radiation model (DCARM) and column coupling acoustic radiation model (CCARM). New approaches are proved to be able to deal with the modal coupling problem efficiently with a good accuracy at a significantly reduced computational cost. Numerical results also indicate that the sound radiation characteristics of a semisubmerged cylindrical shell are quite different from those from the shell fully submerged in fluid. But the far-field sound pressure of a semisubmerged shell fluctuates around that from the shell ideally submerged in fluid. These new approaches can also be used to study the vibroacoustic problems of cylindrical shells partially coupled with fluid.

Evaluation of Aerodynamic Infrasound Radiating From Upwind and Downwind HAWTs

2012 ◽  
Author(s):  
Adrian Sescu ◽  
Abdollah A. Afjeh
Keyword(s):  
Flow Field ◽  
Wind Turbine ◽  
Sound Pressure ◽  
Low Frequency ◽  
Pressure Level ◽  
Frequency Noise ◽  
Far Field ◽  
Acoustic Analogy ◽  
Horizontal Axis Wind Turbines ◽  
Tower Shadow

A Computational Fluid Dynamics tool is used to determine the detailed flow field developing around two-blade horizontal axis wind turbines (HAWT) in downwind and upwind configurations. The resulting flow field around the wind turbine is used to evaluate the low-frequency noise radiating to the far-field, using an acoustic analogy method. The influence of the variation of wind velocity and rotational speed of the rotor to the sound pressure level is analyzed. This paper shows that the tower shadow effect of a downwind configuration wind turbine generates higher aerodynamic infrasound when compared to a corresponding upwind configuration. For validation, a comparison between numerical results and experimental data consisting of sound pressure levels measured from a two-blade downwind configuration wind turbine is presented.

A Technique to Predict the Acoustic Radiation Characteristics of an Automobile Tire

1986 ◽  
Vol 14 (2) ◽  
pp. 102-115 ◽  
Author(s):  
C. Wright ◽  
G. H. Koopmann
Keyword(s):  
Close Agreement ◽  
Sound Pressure ◽  
Acoustic Radiation ◽  
Surface Velocity ◽  
Experimental Measurements ◽  
Far Field ◽  
Radiation Characteristics ◽  
Automobile Tire ◽  
Electrodynamic Vibrator ◽  
Field Sound

Abstract A technique to predict the acoustic radiation characteristics of the predominant structural modes of an automobile tire is presented. A stationary tire is excited by an electrodynamic vibrator and, through conventional modal analysis methods, a description of the surface velocity is obtained. With this information, and a representation of the tire geometry, numerical procedures are used to predict the acoustic surface intensity and field pressure, for a given frequency of interest, based on a Helmholtz integral formulation. Predicted far field sound pressure levels are in close agreement with experimental measurements taken in an anechoic chamber. This provided the necessary validation of the technique.

Modeling and Prediction of Acoustic Resonance for Round Supersonic Jets

2000 ◽  
Author(s):  
A. W. Cary ◽  
W. W. Bower ◽  
A. B. Cain ◽  
E. J. Kershen
Keyword(s):  
Acoustic Waves ◽  
Sound Pressure ◽  
Acoustic Radiation ◽  
Acoustic Resonance ◽  
Supersonic Jets ◽  
Operating Conditions ◽  
Analysis Tool ◽  
Instability Waves ◽  
Round Jets ◽  
Modeling And Prediction

Abstract A computationally rapid analysis tool has been developed to compute the acoustic resonance of off-design supersonic jets known as “screech”. For the case of round jets, the computational model is described which is based on coupling analytical representations of each of the four components of the resonance: 1) the shear layer instability; 2) the vortex/shock interaction; 3) the upstream-propagating acoustic radiation; and 4) the receptive coupling of scattered acoustic waves and instability waves at the nozzle lip. Comparisons among predicted and measured sound pressure levels and frequencies of the resonance are presented for a range of jet operating conditions.

Experimental Study on a Notched Nozzle for Jet Noise Reduction

2011 ◽  
Author(s):  
T. Ishii ◽  
H. Oinuma ◽  
K. Nagai ◽  
N. Tanaka ◽  
Y. Oba ◽  
...  
Keyword(s):  
Experimental Study ◽  
Noise Reduction ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Mixing Layer ◽  
Jet Noise ◽  
Computational Prediction ◽  
Pressure Level ◽  
Far Field ◽  
Noise Sources

This paper describes an experimental study on a notched nozzle for jet noise reduction. The notch, a tiny tetrahedral dent formed at the edge of a nozzle, is expected to enhance mixing within a limited region downstream of the nozzle. The enhanced mixing leads to the suppression of broadband peak components of jet noise with little effect on the engine performance. To investigate the noise reduction performances of a six-notch nozzle, a series of experiments have been performed at an outdoor test site. Tests on the engine include acoustic measurement in the far field to evaluate the noise reduction level with and without the notched nozzle, and pressure measurement near the jet plume to obtain information on noise sources. The far-field measurement indicated the noise reduction by as much as 3 dB in terms of overall sound pressure level in the rear direction of the engine. The use of the six-notch nozzle though decreased the noise-benefit in the side direction. Experimental data indicate that the high-frequency components deteriorate the noise reduction performance at wider angles of radiation. Although the increase in noise is partly because of the increase in velocity, the penetration of the notches into the jet plume is attributed to the increase in sound pressure level in higher frequencies. The results of near-field measurement suggest that an additional sound source appears up to x/D = 4 due to the notches. In addition, the total pressure maps downstream of the nozzle edge, obtained using a pressure rake, show that the notched nozzle deforms the shape of the mixing layer, causing it to become wavy within a limited distance from the nozzle. This deformation of the mixing layer implies strong vortex shedding and thus additional noise sources. To improve the noise characteristics, we proposed a revised version of the nozzle on the basis of a computational prediction, which contained 18 notches that were smaller than those in the 6-notched nozzle. Ongoing tests indicate greater noise reduction in agreement with the computational prediction.

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