scholarly journals The identification of the cylindrical defect position and size by measuring the radiated sound pressure on the plane

2017 ◽  
Vol 230 (4) ◽  
pp. 1337-1345
Author(s):  
S. Iino ◽  
S. Yahiro ◽  
T. Nishikawa ◽  
T. Tsuji
Keyword(s):  
Sound Pressure ◽  
Defect Position ◽  
Radiated Sound

Parametric Studies on Muffler Design With Applications to a Vacuum Pump

1993 ◽  
Author(s):  
B. S. Sridhara
Keyword(s):  
Sound Pressure Level ◽  
Insertion Loss ◽  
Sound Pressure ◽  
Exhaust System ◽  
Pressure Level ◽  
Vacuum Pump ◽  
Expansion Chamber ◽  
Pipe Length ◽  
Parametric Studies ◽  
Radiated Sound

Abstract A computer simulation was employed to perform parametric studies on muffler design. Engine exhaust system parameters such as muffler diameter, source-muffler pipe length, number of mufflers, series and parallel installation of mufflers, and the source and termination impedances were considered during the studies. The muffler insertion loss and radiated sound pressure level were predicted for several values of each parameter. An acoustic model consisting of a lumped source-muffler-termination system was used. A scheme was developed using the pressure source model to predict the radiated sound pressure and a simplified expression for the predicted quantity was obtained as a sum of the measured, plane wave and monopole terms. The relationship between the insertion loss and radiated sound pressure level was established for a given set of conditions. A vacuum pump was used as the sound source. An expansion chamber was used as a muffler.

Reduction of the Sound Pressure Radiated by a Submarine by Isolation of the End Caps

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Mauro Caresta ◽  
Nicole J. Kessissoglou
Keyword(s):  
Sound Pressure ◽  
Low Frequency ◽  
Axial Direction ◽  
Radial Component ◽  
Axial Motion ◽  
Low Frequencies ◽  
End Caps ◽  
Passive Isolation ◽  
Radiated Sound ◽  
Finite Cylindrical Shell

A passive isolation approach to reduce the sound pressure radiated by a submarine is presented. The submerged vessel is modeled as a stiffened cylindrical hull partitioned by bulkheads and with two end caps of conical shape. Fluctuating forces from the propeller are transmitted to the hull through the shaft and a rigid foundation, resulting in axisymmetric excitation of the hull. The hull surface motion is mainly in the axial direction with a small radial component due to the coupling between the two orthogonal shell displacements. The sound pressure resulting from the axial motion is radiated from the end caps of the submarine. This work investigates reduction of the far field sound pressure by passive isolation of the end caps from the main hull. Isolation of the axial motion of the end caps from the cylindrical hull results in significant reduction of the radiated sound at low frequencies. The fluid loading approximation for a finite cylindrical shell in the low frequency range is also discussed.

Consistent Formulation of Sound Radiation From Arbitrary Structure

1975 ◽  
Vol 42 (2) ◽  
pp. 295-300 ◽  
Author(s):  
J. J. Engblom ◽  
R. B. Nelson
Keyword(s):  
Sound Pressure ◽  
Special Problem ◽  
Acoustic Medium ◽  
Integral Forms ◽  
Equilibrium Relationship ◽  
Modes Of Vibration ◽  
Radiated Sound ◽  
Equilibrium Relationships ◽  
Consistent Formulation ◽  
Quadratic Approximations

A refined and efficient approach is presented for determining the radiated sound pressure levels in an infinite acoustic medium produced by a closed structure undergoing harmonic vibratory motion. Refined acoustic and equilibrium relationships are developed and quadratic approximations are used to define the acoustic variables on the radiating surface. Efficiencies are inherent in the modal approach utilized to define an equilibrium relationship and in the treatment of improper integral forms. Examples include the special problem of a finite cylindrical cavity for which uniform radial velocity is specified. Also investigated is a thin elastic sphere for which particular modes of vibration are specified.

scholarly journals Effects of jet angle on harmonic structure of sound radiating from the flute

Acta Acustica ◽  
2021 ◽  
Vol 5 ◽  
pp. 11
Author(s):  
Kimie Onogi ◽  
Hiroshi Yokoyama ◽  
Akiyoshi Iida
Keyword(s):  
Flow Rate ◽  
Sound Pressure ◽  
Pressure Level ◽  
Harmonic Structure ◽  
Relative Height ◽  
Hot Wire ◽  
Third Harmonic ◽  
Edge Distance ◽  
Radiated Sound ◽  
Human Player

For an isolated flute head joint, the effects of jet angle on harmonic structure of a single note are investigated within the practical range for human players. The mechanisms of these effects are discussed on the basis of both the radiated sound and the flow field measured with a hot-wire anemometer. The blowing parameters, viz., jet angle (angle between jet direction and window), jet offset (relative height of jet direction from the edge), lip-to-edge distance, and flow rate, were varied independently by using an artificial blowing device based on measured conditions for a human player, where the jet direction is defined as that measured without the head joint. The radiated sound revealed that jet angle varied the differential sound pressure level of the second to third harmonic (ΔSPL) less than jet offset, however, as much as flow rate and more than lip-to-edge distance. The spatial distribution of jet fluctuation center showed that, with increasing jet angle (the jet direction approaches vertical to the window), the jet deflected more inside, so that the actual jet offset was estimated to be further inside. The variation of ∆SPL with jet angle seems to be caused mainly by this shift in the actual jet offset.

Finite Element Simulation of an Automotive Brake Rotor With Metallic Damping Inserts

2010 ◽  
Author(s):  
Shung H. Sung ◽  
M. David Hanna ◽  
James G. Schroth
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Sound Pressure ◽  
Radiated Noise ◽  
Press Fit ◽  
Modal Damping ◽  
Brake Rotor ◽  
Radiated Sound ◽  
Automotive Brake ◽  
Element Method

A finite element method is developed for simulating the performance of an automotive brake rotor with metallic inserts that are used to dampen the vibration and radiated noise response. The metallic inserts are located in slots that are cast at the edge of the rotor circumference between the two rotor surfaces. Three different rotor configurations are evaluated: (a) an undamped solid rotor, (b) a damped rotor with an unconstrained press-fit metallic insert, and (c) a damped rotor with a constrained cast-in coated metallic insert. Comparisons of the predicted versus measured rotor surface vibration and radiated sound pressure are made to evaluate the effect of the insert and the accuracy of the finite element method. The comparisons show that significant modal damping of the rotor vibration and radiated noise can be achieved through the use of the coated metallic insert. A methodology is developed and applied to evaluate the damping of different metallic inserts and coatings from only the radiated sound pressure response.

scholarly journals Evaluation and Improvement of the Sound Quality of a Diesel Engine Based on Tests and Simulations

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 777 ◽  
Author(s):  
Zhengwei Yang ◽  
Huihua Feng ◽  
Bingjie Ma ◽  
Ammar Abdualrahim Alnor Khalifa
Keyword(s):  
Diesel Engine ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Subjective Evaluation ◽  
Sound Field ◽  
Sound Quality ◽  
Pressure Level ◽  
Sound Power ◽  
Improvement Strategy ◽  
Radiated Sound

Traditional acoustic evaluation of a diesel engine generally uses the A-weighted sound pressure level (AWSPL) and radiated sound power to assess the noise of an engine prototype present in an experiment. However, this cannot accurately and comprehensively reflect the auditory senses of human subjects during the simulation stage. To overcome such shortage, the Moore–Glasberg loudness and sharpness approach is applied to evaluate and improve the sound quality (SQ) of a 16 V-type marine diesel engine, and synthesizing noise audio files. Through finite element (FE) simulations, the modes of the engine’s block and the average vibrational velocity of the entire engine surface were calculated and compared with the test results. By further applying an automatically matched layer (AML) approach, the engine-radiated sound pressure level (SPL) and sound power contributions of all engine parts were obtained. By analyzing the Moore–Glasberg loudness and sharpness characteristics of three critical sound field points, an improvement strategy of the oil sump was then proposed. After improvement, both the loudness and sharpness decreased significantly. To verify the objective SQ evaluation results, ten noise audio clips of the diesel engine were then synthesized and tested. The subjective evaluation results were in accordance with the simulated analysis. Therefore, the proposed approach to analyze and improve the SQ of a diesel engine is reliable and effective.

Acoustic Similarity Laws for Fans

1982 ◽  
Vol 104 (2) ◽  
pp. 162-168 ◽  
Author(s):  
W. Neise ◽  
B. Barsikow
Keyword(s):  
Reynolds Number ◽  
Sound Pressure ◽  
Experimental Results ◽  
Acoustic Similarity ◽  
Fan Noise ◽  
Working Fluids ◽  
Centrifugal Fans ◽  
Noise Data ◽  
Radiated Sound ◽  
Similarity Laws

In order to verify experimentally acoustic similarity laws for fans, experiments were made with three, dimensionally similar centrifugal fans of 140, 280, and 560 mm impeller diameter. The fans were connected to anechoically terminated discharge ducts. It is shown that the influence of the Reynolds number on the radiated sound pressure is negligible within 1.4•105 ≦ Re ≦ 2.2•106, which is the range covered by the measurements. This is in agreement with earlier studies in which the Reynolds number was varied from 1.4•104 to 4.5•105. From the experimental results it is concluded that fan noise data that are taken on model fans can be extrapolated to other dimensionally similar fans of different size for arbitrary fan speeds and working fluids, provided that the operating condition and the measurement position are the same.

CAE Technology Applied to Range Hood’s Noise Control and Optimization Design

2011 ◽  
Vol 338 ◽  
pp. 543-546
Author(s):  
Hu Yu ◽  
Hong Hou ◽  
Liang Sun
Keyword(s):  
Sound Pressure Level ◽  
Optimization Design ◽  
Sound Pressure ◽  
Element Model ◽  
Pressure Level ◽  
Sound Power ◽  
Radiated Noise ◽  
Radiated Sound ◽  
Cae Technology ◽  
Radiated Sound Power

In this study we use the CAE technology to compute and reduce the radiated noise of range hood. First, a finite element model of a typical range hood is created using Hypermesh. Then, the surface particle velocity is carried out in Nastran, and the radiated noise is calculated by Sysnoise. Finally, the DOE-based structural optimization is preformed using iSIGHT-FD, in which the sound pressure level at four sensitive points and the radiated sound power are selected as the objective function and the thickness of four panels are adopted as design variable. In addition, the weight of the range hood as a constraint is kept no more than its original weight. As a result, a maximum radiated sound power reduction of 3.66W and a maximum sound pressure level reduction of 4.7 dB are successfully achieved. It shows the CAE technology is a very efficient and effective method for reducing radiated noise.

Near-Field Acoustic Holography of Cyclostationary Sound Field

2013 ◽  
Vol 631-632 ◽  
pp. 1318-1323
Author(s):  
Min Peng
Keyword(s):  
Time Series ◽  
Sound Pressure ◽  
Near Field ◽  
Sound Field ◽  
Rotating Machinery ◽  
Stationary Field ◽  
Acoustic Holography ◽  
Complex Sound ◽  
Radiated Sound ◽  
Slice Method

The radiated sound field of rotating machinery or reciprocating machinery has a significant periodically time-variant nature. This is a kind of non-stationary sound field and called cyclostationary sound field. In the conventional planar near-field acoustic holography(PNAH), this kind of sound field is treated as stationary field, so the information relating to the change of frequency with time will be loss inevitably. In this article, the cyclic spectral density(CSD) instead of the complex sound pressure was adopted as reconstructing physical quantity in the PNAH, and the cyclostationary PNAH(CPNAH) technique was proposed. Meanwhile, focusing on the calculation complex of CSD and the accuracy of the cyclic nature extracted, the gathering slice method of CSD was proposed by referring time aliasing methods on time series. The experiment results illustrate that the cyclic nature of cyclostationary sound field may be extracted directly and the location of the source determined exactly as well.

Acoustic emission by a vortex ring passing near a sharp wedge

1994 ◽  
Vol 445 (1923) ◽  
pp. 141-155 ◽  
Keyword(s):  
Vortex Ring ◽  
Sound Speed ◽  
Sound Pressure ◽  
Time History ◽  
Wave Profile ◽  
Dimensionless Time ◽  
Shortest Distance ◽  
History Of ◽  
Radiated Sound ◽  
Special Case

The acoustic field is analysed for a vortex ring passing near a sharp wedge of span angle ϕ 0 at low Mach numbers. This includes the half-plane as a special case ( ϕ 0 = 0), which has received detailed consideration in the literature. Let U be the ring’s velocity, c the sound speed, and L the shortest distance of the vortex ring from the edge of the wedge. The sound pressure at large distances x is found to be proportional to c -π/ ϕ 1 U π/ ϕ 1 +2 L -2 x -1 , while the time history of the wave profile is in the form of fractional derivative D t ˆ π/ ϕ 1 g ( t ˆ ) with ϕ 1 = 2π - ϕ 0 , where t ˆ is dimensionless time and g ( t ˆ ) is a smooth function of t ˆ . The directivity of the radiated sound is found to be given by cos ((π/ ϕ 1 ) ϕ i ) (sin θ i ) π/ ϕ 1 , where ( θ i , ϕ i ) denotes the direction of observation. An additional factor, appearing as (sin θ p ) π/ ϕ 1 +2 , characterizes the effect of the angle θ p , formed between the path of the vortex ring and the edge of the sharp wedge.

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