scholarly journals Sound Radiation Characteristics of a Rectangular Duct with Flexible Walls

2016 ◽  
Vol 2016 ◽  
pp. 1-15
Author(s):  
Praveena Raviprolu ◽  
Nagaraja Jade ◽  
Venkatesham Balide
Keyword(s):  
Analytical Model ◽  
Power Level ◽  
Sound Radiation ◽  
Rectangular Duct ◽  
Radiation Characteristics ◽  
Vibration Displacement ◽  
Flexible Walls ◽  
Radiated Sound ◽  
Radiated Sound Power ◽  
Element Method

Acoustic breakout noise is predominant in flexible rectangular ducts. The study of the sound radiated from the thin flexible rectangular duct walls helps in understanding breakout noise. The current paper describes an analytical model, to predict the sound radiation characteristics like total radiated sound power level, modal radiation efficiency, and directivity of the radiated sound from the duct walls. The analytical model is developed based on an equivalent plate model of the rectangular duct. This model has considered the coupled and uncoupled behaviour of both acoustic and structural subsystems. The proposed analytical model results are validated using finite element method (FEM) and boundary element method (BEM). Duct acoustic and structural modes are analysed to understand the sound radiation behaviour of a duct and its equivalence with monopole and dipole sources. The most efficient radiating modes are identified by vibration displacement of the duct walls and for these the radiation efficiencies have been calculated. The calculated modal radiation efficiencies of a duct compared to a simple rectangular plate indicate similar radiation characteristics.

Sound Radiation Response of a Rectangular Plate Having a Side Crack of Arbitrary Length, Orientation, and Position

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Tanmoy Bose ◽  
Amiya R. Mohanty
Keyword(s):  
Rectangular Plate ◽  
Ritz Method ◽  
Sound Radiation ◽  
Radiation Efficiency ◽  
Sound Power ◽  
Cracked Plate ◽  
Side Crack ◽  
Radiated Sound ◽  
Radiated Sound Power ◽  
Element Method

Here, sound radiation characteristics of a rectangular plate having a side crack of different crack lengths, orientations, and positions are studied considering clamped boundary conditions. First, a free and forced vibration response analysis of a cracked plate is done using the Ritz method. Orthogonal polynomials are used for faster convergence and some corner functions are used to generate the effect of a crack. Radiated sound power and radiation efficiency of the cracked plate are computed by the quadruple integration. A convergence test of radiation efficiency is carried out to fix the number of polynomials and corner functions in the analysis. It is found that the radiation efficiency and radiated sound power computed by the Ritz method are close to the same obtained from the boundary element method (BEM). The natural frequencies computed using the Ritz method are also found to be close to that obtained from the finite element method (FEM). The radiation efficiency curves of different modes are shown for a change in crack length, orientation and position. Finally, the variations of normalized sound power are shown to be due to a change in the crack parameters.

scholarly journals Faster Calculation of the Low-Frequency Radiated Sound Power of Underwater Slender Cylindrical Shells

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Rui Tang ◽  
He Tian ◽  
Dajing Shang
Keyword(s):  
Cylindrical Shell ◽  
Cylindrical Shells ◽  
Low Frequency ◽  
Sound Radiation ◽  
Sound Power ◽  
Radiation Characteristics ◽  
Calculation Process ◽  
Radiated Sound ◽  
Stiffened Cylindrical Shells ◽  
Radiated Sound Power

Based on the fact that beam-type modes play the main role in determining the sound radiation from an underwater thin slender (length-to-radius ratio L/a>20) elastic cylindrical shell, an equivalent-beam method is proposed for calculating the low-frequency radiated sound power of underwater thin slender unstiffened and stiffened cylindrical shells. The natural bending frequencies of the cylindrical shell are calculated by analytical and numerical methods and used to solve equivalent Young’s modulus of the equivalent beam. This approach simplifies the vibration problem of the three-dimensional cylindrical shell into that of a two-dimensional beam, which can be used to simplify the calculation process of radiated sound power. Added mass is used to approximate the fluid-structure coupling, further simplifying the calculation process. Calculation examples of underwater simply supported unstiffened and stiffened cylindrical shells verify the proposed method by comparison with analytical and numerical results. Finally, the effects of the size and spacing of the stiffeners on the sound radiation characteristics of underwater free-free stiffened cylindrical shells are discussed. The proposed method can be extended to the rapid calculation of the sound radiation characteristics of underwater slender complex cylindrical shells in the low-frequency range.

Sound Radiation Characteristics of Lightweight Roof Constructions Excited by Rain

1994 ◽  
Vol 1 (4) ◽  
pp. 249-270 ◽  
Author(s):  
Hiromi Suga ◽  
Hideki Tachibana
Keyword(s):  
Transmission Loss ◽  
Power Level ◽  
Sound Radiation ◽  
Sound Intensity ◽  
Sound Power ◽  
Radiation Characteristics ◽  
Natural Rainfall ◽  
Artificial Rainfall ◽  
Sound Power Level ◽  
Measurement Results

In order to investigate the sound radiation characteristics of lightweight roof constructions when excited by rainfall, an artificial rainfall apparatus was constructed to simulate natural rainfall conditions. From the measurement results, it can be seen that the facility developed is practically applicable for the examination of the sound radiation characteristics of rain noise. It was therefore used in the measurement of sound power of 20 lightweight roofs. In addition, the relationship between sound power level and sound transmission loss measured by the sound intensity method was investigated statistically. As a result, it has been shown that a linear relationship exists between them and there is a possibility of estimating the sound power level from the transmission loss.

Vibroacoustic Optimization of Mechanical Structures: A Controlled Random Search Approach

2012 ◽  
Vol 622-623 ◽  
pp. 158-161 ◽  
Author(s):  
Mostafa Ranjbar ◽  
Steffen Marburg
Keyword(s):  
Random Search ◽  
Power Level ◽  
Search Method ◽  
Frequency Range ◽  
Controlled Random Search ◽  
Sound Power Level ◽  
Specific Frequency ◽  
Radiated Sound ◽  
Search Approach ◽  
Radiated Sound Power

A combination of controlled random search method and geometry modification concept is used to minimize the root mean square level of structure borne sound for a model. The structure is a rectangular plate made of steel. A specific frequency range for this porpuse is considered. The results show that this approach could produce significant reduction in the value of radiated sound power level of the structure within a limited time.

An Active Control Strategy for Achieving Weak Radiator Structures

1994 ◽  
Vol 116 (1) ◽  
pp. 31-37 ◽  
Author(s):  
K. Naghshineh ◽  
G. H. Koopmann
Keyword(s):  
Control Strategy ◽  
Power Level ◽  
Wave Number ◽  
Sound Power ◽  
Plane Wave Incident ◽  
Supersonic Region ◽  
Radiated Sound ◽  
Control Forces ◽  
Structural Mobility ◽  
Radiated Sound Power

A general control strategy is presented for active suppression of total radiated sound power from harmonically excited structures based on the measurement of their response. Using the measured response of the structure together with knowledge of its structural mobility, an equivalent primary excitation force is found at discrete points along the structure. Using this equivalent primary force and performing a quadratic optimization of the power radiated from the structure, a set of control forces is found at selected points on the structure that results in minimum radiated sound power. A numerical example of this strategy is presented for a simply supported beam in a rigid baffle excited by a harmonic plane wave incident at an oblique angle. A comparison of the response of the beam with and without control forces shows a large reduction in the controlled response displacement magnitude. In addition, as the result of the action of the control forces, the magnitude of the wave number spectrum of the beam’s response in the supersonic region is decreased substantially. The effect of the number and location of the actuators on reductions in sound power level is also studied. The actuators located at the anti-nodes of structural modes within the supersonic region together with those lcoated near boundaries are found to be the most effective in controlling the radiation of sound from a structure.

ENFORCING RECIPROCITY IN NUMERICAL ANALYSIS OF ACOUSTIC RADIATION MODES AND SOUND POWER EVALUATION

2012 ◽  
Vol 20 (03) ◽  
pp. 1250005 ◽  
Author(s):  
HERWIG PETERS ◽  
NICOLE KESSISSOGLOU ◽  
STEFFEN MARBURG
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Acoustic Radiation ◽  
Sound Power ◽  
Impedance Matrix ◽  
Radiated Sound ◽  
The Asymmetry ◽  
Power Evaluation ◽  
Radiated Sound Power ◽  
Element Method

By identifying the efficiently radiating acoustic radiation modes of a fluid loaded vibrating structure, the storage requirements of the acoustic impedance matrix for calculation of the sound power using the boundary element method can be greatly reduced. In order to compute the acoustic radiation modes, the impedance matrix needs to be symmetric. However, when using the boundary element method, it is often found that the impedance matrix is not symmetric. This paper describes the origin of the asymmetry of the impedance matrix and presents a simple way to generate symmetry. The introduction of additional errors when symmetrizing the impedance matrix must be avoided. An example is used to demonstrate the behavior of the asymmetry and the effect of symmetrization of the impedance matrix on the sound power. The application of the technique presented in this work to compute the radiated sound power of a submerged marine vessel is discussed.

Relation Between Structural Intensity-Based Scalars and Sound Radiation Using the Example of Plate-Rib Models

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Clarissa Schaal ◽  
Johannes Ebert ◽  
Joachim Bös ◽  
Tobias Melz
Keyword(s):  
Objective Function ◽  
Energy Flow ◽  
Vibrational Energy ◽  
Sound Radiation ◽  
Specific Region ◽  
Sound Power ◽  
Structural Intensity ◽  
Radiated Sound ◽  
Very High ◽  
Radiated Sound Power

The ability of the structural intensity (STI) to predict changes in the sound radiation of structures due to geometric modifications is investigated using the academic example of plate-rib models. All models consist of the same plate and are modified by attaching a rib, whose position, orientation, and length are varied. Various scalar quantities are derived from the STI and quantitatively compared to the equivalent radiated sound power (ERP) for each model. Based on this comparison the relation between the STI-based scalars and the ERP is studied to determine an STI-based scalar that can serve as the objective function for numerical structural optimizations. The influence of the rib parameters on the most promising STI-based scalar is analyzed by means of a variance-based sensitivity analysis. The STI pattern of those models with very high and very low ERP values are additionally analyzed to describe the characteristics of STI. The results of this study indicate that the STI pattern of models with low ERP has paths and vortices that can be more clearly identified compared to those in models with high ERP. The angular orientation of the rib has by far the highest influence on changes in STI and ERP. The results reveal a correlation between the energy flow into a specific region of a structure, an STI-based scalar, and the ERP. Therefore, the vibrational energy flow can indeed serve as an objective function for numerical structural optimizations aiming at reducing the sound radiation.

Optimized Perforation Schemes in Railway Wheels Toward Acoustic Radiation Mitigation

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
J. Gutiérrez-Gil ◽  
X. Garcia-Andrés ◽  
J. Martínez-Casas ◽  
E. Nadal ◽  
F. D. Denia
Keyword(s):  
Power Level ◽  
Sound Power ◽  
Noise Mitigation ◽  
Railway Network ◽  
Potential Shape ◽  
Radiated Sound ◽  
Railway Wheels ◽  
Wheel Vibration ◽  
The Web ◽  
Radiated Sound Power

Abstract Rolling noise emitted by railway wheels is a problem that affects human health and limits the expansion of the railway network. It is caused by the wheel vibration due to the wheel-rail contact force, and it is important in almost all the vehicle velocity range. The minimization of noise radiation associated with changes on the wheel web is discussed in this work, focusing on potential shape modifications in existing wheels in the form of a perforation distribution over the web. Such a post-manufacturing technique is a cost-effective solution that can be performed in a relatively short term. The implemented objective function is directly related to the overall radiated sound power, which is minimized using a genetic algorithm-based optimizer. In the acoustic model, radiation efficiencies are approximated to unity, the accuracy of this assumption being also studied in the work. The results reflect that an optimized distribution of perforations on the web of a railway wheel can reduce the total sound power level, by about 5 dB(A) and 2 dB(A) for curved and straight web, respectively. The mitigation of the radiated sound power is due to the fact that certain wheel vibration modes are modified and shifted to other frequencies where they are less excited. Finally, the relevance of the cross-sectional curvature of the web is explored by studying two different web geometries, suggesting that it can strongly influence the noise mitigation effects of the perforation pattern.

Preliminary Investigation on the Perforated Panel Mobility Using Finite Element Method

2013 ◽  
Vol 471 ◽  
pp. 341-346
Author(s):  
Azma Putra ◽  
A. Rivai ◽  
Wai C. Mun ◽  
Noryani Muhammad
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Analytical Model ◽  
Noise Control ◽  
Preliminary Investigation ◽  
Sound Radiation ◽  
Control Measures ◽  
Hole Size ◽  
Panel Stiffness ◽  
Element Method

Introduction of holes into plat-like structures is commonly found as one of practical noise control measures to reduce sound radiation. However, perforation into the panel also reduces the panel stiffness and hence increases its vibration. Since the discussion and also the analytical model to quantify this effect are lacking, this paper discusses the dynamics of a perforated panel from the results obtained using Finite Element Method (FEM). Different hole geometries are simulated to investigate their effect on the plate mobility. It is found that increasing the perforation ratio increases the plate mobility particularly at off-resonance peaks. The effect of hole size and number are also discussed in this report.

Sign in / Sign up

Export Citation Format

Share Document