Дисертації з теми "Acoustics and noise control (except architectural acoustics)"
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Saunders, William R. "On the use of modern control theory for active structural acoustic control." Diss., This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-07282008-134205/.
Повний текст джерелаHazard, Laurent. "Design of viscoelastic damping for noise & vibration control: modelling, experiments and optimisation." Doctoral thesis, Universite Libre de Bruxelles, 2007. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210772.
Повний текст джерелаpartition of unity functions with arbitrary chosen enrichment functions. Polynomial enrichment leads to the generation of high-order polynomial shape functions and is therefore similar to a p-FEM technique. Numerical examples illustrate the use of both PUFEM Mindlin plate elements and interface elements for the simulation of viscoelastic sandwich structures.
Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished
Ribeiro, Rodrigo Scoczynski. "Avaliação do desempenho acústico de um sistema de construção modular: estudo de caso." Universidade Tecnológica Federal do Paraná, 2015. http://repositorio.utfpr.edu.br/jspui/handle/1/1303.
Повний текст джерелаThe objective of this study is evaluate the modular and industrialized building system’s acoustic performance through the simplified field method indicated by ABNT NBR 15575-4:2013 and ISO 10052: 2004, analyzing the internal and external vertical seals for air noise insulation and comparing with previous analyzes in other approaches. The world construction industry is in a dedicated time to the pursuit and implementation of sector modernization strategies in order to reduce costs and minimize waste, invested in sustainable buildings. It’s is necessary studies based on the parameters of NBR 15575-4: 2013 for the proper characterization of building technologies that emerge and are still new to the sector. The standard implies a series of requirements and recommendations, such as the acoustic comfort, which will be addressed in this work. The methodology used was based on the simplified method guided by ISO 10052: 2004. Two buildings were analyzed, with 40,0m2 each. One of them is a two-story house, and the other is a ground floor building. Measurements of sound pressure levels were made in the rooms and on the frontages, and measurements of the reverberation time of rooms. After the measurements were made analyzes with test "t" student. Compared to the standards of other countries, it was realized that the ABNT NBR 15575-4: 2013 has soft values, and that even so, the current Brazilian construction techniques, for the most part, can not reach them. Through these results, it was noticed an efficiency about the isolation airnoise in modular and industrialized buildings compared to buildings of other construction techniques. It follows, then, that the floor and the ground floor building comply with the performance levels established by ABNT NBR 15575-4: 2013.
(8028554), Yiming Wang. "PROPAGATION OF EN-ROUTE AIRCRAFT NOISE." Thesis, 2019.
Знайти повний текст джерелаTo provide a more accurate prediction of en-route aircraft noise, we derived the analytic asymptotic solution of the sound field above a non-locally reacting ground due to a moving point source and a line source using the methods of the steepest descent and a Lorentz transform. The model predicts a much more accurate result for sound field above "soft" grounds, such as a snow-covered ground and sand-covered ground. At the same time, we derived a fast numerical algorithm based on Levin’s collocation for the prediction of the sound field in the presence of a temperature gradient, which can be applied to a wide range of acoustic problems involving integration. The achievements recorded in this thesis can be used to predict the sound field generated by aircraft, trains, and vehicles with a subsonic moving speed. In addition,
the model can be used for detection and design of moving sound source.
(9755876), Guochenhao Song. "Annoyance thresholds of tones in noise as related to building services equipment." Thesis, 2020.
Знайти повний текст джерелаTonal sounds are a particular problem of concern in building environments, arising from the widely used rotating machinery (e.g., compressors, fans, motors, trans- formers, etc.). In the recent trend of designing and manufacturing high-performance building mechanical systems, higher output power and higher rotation speed are pursued, this inevitably results in a more severe noise problem, since the equipment noise not only becomes louder but also shifts to a higher frequency region (which, in most cases, results in a poorer sound quality due to the shift in spectral balance and tonal components moving into the frequency regions where people are most sensitive to tones). Tonal sounds from rotary machines can be annoying, even at relative low levels.
Currently, noise criteria guidelines in Chapter 48 of the ASHRAE HVAC Applications Handbook can be used to design the building mechanical system, but this does not apply well for tonal noise. Reducing the limit for noise with perceptible tones is one common strategy in the industry. However, it’s not adequate for some cases, over-design in others. Thus, an adequate understanding of the annoyance threshold of tonal noises associated with building services equipment is valuable technical information not only in the design and manufacture of machines but also in the development of noise regulations related to building services equipment.
This research aims to develop a sound quality model that cooperates with sound level and tonalness and relates tonal building noises to the perceived annoyance.
(6417068), Dan Ding. "Implementation of Microphone Array Processing Techniques on A Synthetic Array for Fluid Power Noise Diagnostics." Thesis, 2019.
Знайти повний текст джерела(9193604), Wesaam Lepak. "DEVELOPMENT OF SOURCE-PATH MODELS TO SYNTHESIZE PRODUCT SOUNDS OF AN OUTDOOR HVAC UNIT." Thesis, 2020.
Знайти повний текст джерела(7500887), Yutong Xue. "MODELING AND DESIGN METHODOLOGIES FOR SOUND ABSORBING POROUS MATERIALS WHEN USED AS LAYERED VIBRATION DAMPERS." Thesis, 2019.
Знайти повний текст джерела(8085548), Weimin Thor. "Application of Statistically Optimized Near-field Acoustical Holography (SONAH) in Cylindrical Coordinates to Noise Control of a Bladeless Fan." Thesis, 2019.
Знайти повний текст джерела(7046483), Ang Li. "Characterization of Aerodynamic and Aeroacoustic Performance of Bladeless Fans." Thesis, 2019.
Знайти повний текст джерела(9750938), Leandro Henschel Danes. "COMPUTATIONAL METHODS FOR DESIGNING NEW PASSIVE FLUID BORNE NOISE SOURCE REDUCTION STRATEGIES IN HYDRAULIC SYSTEMS." Thesis, 2020.
Знайти повний текст джерелаHydraulic systems have many applications in the construction, transportation, and manufacturing sectors. Recent design trends involve systems with higher working pressures and more compact systems, which are advantageous because of power density increase. However, these trends imply higher forces and larger vibration amplitudes while having lesser mass and damping, leading to higher noise levels. Meanwhile, hydraulic machinery started prospecting new applications with tighter noise regulations, a trend which was also pushed by the electrification tendency in several fields of transportation and agriculture. One method to attain noise mitigation is passive-noise canceling techniques have the advantage of not introducing energy to the system. This approach arranges pressure ripple waves in a destructive pattern by projecting a hydraulic circuit's geometry, configuration, and features.
This dissertation aims to predict fluid-borne noise sources and investigate passive noise-canceling solutions for multiple operations conditions targeting to impact many hydraulic systems and a broad range of operating conditions. Primarily a coupled system model strategy that includes a one-dimensional line finite element model is developed. The line model predicts pressure wave generation and propagation. The model features versatility since parameters like line diameter and material can be discretized node by node. Simulations are compared to measured data in a realistic novel hydraulic hybrid transmission for validation.
Subsequently, an extensive numerical investigation is performed by setting fixed parameters along the hydraulic lines' length and comparing several isolated geometric properties in simulation. The developed line model is also used to study the influence of line features such as diameter and extent of the conduit. Cost-effective and simple passive solution solutions such as Quincke tubes (parallel lines), expansion chambers, and closed branches are selected and investigated on simulation. Four target pressure ripples are chosen as indicators for summarizing passive line elements behavior. The frequency-domain behavior of the pressure ripple peaks regarding the line's length is identified and isolated in simulation at the 50-5000Hz frequency spectrum. An experiment test rig is designed to implement these solutions and the experiments show three developed passive elements as practical and effective solutions for reducing fluid borne noise sources. The selected designs yielded noise source attenuation over most of the frequency spectrum measured with piezoelectric pressure variation sensors and accelerometers in different positions in the hydraulic circuit. Sound pressure measurements detected reductions over 3dB in the best cases.
Also, a passive interference approach based on the principle of secondary source flow ripple cancellation was conceptualized, modeled, and implemented in a tandem axial-piston unit. The strategy consists of setting the phase between the two synchronous units to accomplish destructive interference in targeted unit harmonics. Two indexing strategies are investigated first analytically and then on simulation. One of the indexing strategies was implemented in a pre-existent commercial axial-piston tandem unit. Experiment results confirmed effectiveness for the first and third unit’s harmonics, where reductions over 15dB on pressure ripple were measured.
Finally, a fluid-structure interaction based on the poison coupling principle is developed using the method of characteristics. Transfer functions of the pipeline accelerations versus the pressure ripples on lines calculated on simulation and later obtained experimentally to highlight ta critical vibration band from 2000Hz to 3000Hz with high acceleration response.
(6622235), Hyunjun Shin. "Weight Minimization of Sound Packages by Balancing Absorption and Transmission Performance." Thesis, 2019.
Знайти повний текст джерелаGenerally, heavier noise control treatments are favored over lighter ones since heavier acoustical materials tend to insulate (block) noise sources more effectively than do lighter materials. In automotive applications, however, heavier materials cannot always be adopted because of concerns over the total weight of the vehicle. Thus, it would be useful to identify lightweight acoustical treatments that can mitigate vehicle interior noise. Automotive sound packages have both absorption and barrier characteristics, and there is inevitably a trade-off between these two. Therefore, it is important to study the exchange between the absorption and transmission of acoustical materials particularly as it pertains to weight. Here, a procedure based on plane wave analysis is described that can be used to identify weight reduction opportunities by adjusting the acoustical properties of a generic sound package, consisting of a fibrous layer and a flexible microperforated panel surface treatment, so that it meets a target sound pressure level in a downstream interior space. It has been found, for the configuration studied here, that there are lightweight sound package configurations that can maintain acoustical performance equivalent to that of heavier noise treatments, and further, it has been found that the lightest treatments tend to favor barrier performance rather than absorption. Further, the impact of acoustical leaks has been considered, and it has been found that even very small leaks can result in a very substantial weight penalty if a specified level of acoustical performance is to be ensured. Further, the impact of changing the underlying panel mass and altering the frequency weighting used in the optimization process has also been considered.
The optimizer used in the proposed procedure requires considerable calculation time; hence, the acoustic pressure calculation time needs to be minimized to enhance the efficiency of the solution process. Thus, the transfer matrix method (TMM) for a two-dimensional case was used to calculate the interior acoustic pressure for a simple geometry as a starting point in the process of identifying the minimum-weight sound packages. The TMM is a widely used analytical approach to predicting the sound pressure (and particle velocity) for a system that can be represented as a series of subsystems. Although the TMM can offer fast and simple calculations for the acoustic system, its application is limited to a plane-wave-based model. Thus, the TMM is not the best option for the acoustic pressure prediction in a complex geometry such as a vehicle interior, that involves non-planar wave propagation. Therefore, a hybrid TMM-FEA method is proposed in this research to evaluate the acoustical performance of the sound package in more complex geometries (here, a vehicle-like cavity). So, in this research, the TMM was introduced to obtain the initial solutions that can be used in conjunction with the FEA tool to calculate the sound pressure field in the complex geometry case. The correlation between the results of these two approaches was then analyzed to develop a space-averaged pressure prediction model for various absorptive cases in the interior space. Finally, this SAP prediction model was used to generate an acoustic map that can be used to graphically estimate the SAPs in the complex geometry case.
In order to validate the usage of the developed equation for different sets of boundary conditions, several case studies were performed to study the effects of the surface impedance arrangements, geometrical shapes, and, lastly, the presence of extra features in the interior space. Finally, the SAP difference between the area near the driver’s right ear and the total interior cavity was studied to show that the SAP of the total cavity can be adjusted to evaluate the acoustic performance of the sound packages along the lines of conventional industry practice.
(8877470), Michael John Willi Butzen. "Design of Test Section for Modulating Heat Flux Using Acoustic Streaming in Narrow Channel Experiments." Thesis, 2021.
Знайти повний текст джерелаAircraft engines require lightweight efficient thermal management devices to improve engine performance at high pressure ratios. Acoustic streaming can provide a viable, lightweight solution to improve the heat exchanger capacity with a reduced drag penalty within engine heat exchangers. This project develops a test section that will experimentally characterize the effect of acoustic streaming on the unsteady heat flux and shear stress within a narrow channel. This is accomplished by careful selection of measurement techniques to monitor the steady and unsteady properties of the flow and iteratively designing the test section with CFD support to converge to an optimal test model. Using CFD support to revise each iteration reduces the experimental cost of developing an effective geometry.
Pressure taps and K-type thermocouples are used to monitor the total inlet pressure and temperature as well as the wall surface pressure and temperature. Optical shear stress sensors are selected to monitor the unsteady wall shear stress. A thin film sensor array is designed for high frequency wall temperature measurements which serve the boundary condition for a 1-D heat flux analysis to determine the unsteady heat flux through the wall. The test model consists of two hollow Teflon airfoils that create a narrow channel within a larger flow area. The airfoils create three flow paths within the wind tunnel test section and the area ratio between the measured flow and the bypass flow controls the Mach number of within the measured flow channel. The acoustic waves drive acoustic streaming and are generated by a Rossiter Cavity with L/D =2 which produces pressure oscillations with dominant frequency of 8 kHz in a Mach 0.8 flow.
The test geometry successfully achieves Mach 0.8 flow and the 8 kHz signal [BMJW1] from the Rossiter cavity. The successful commissioning sets the stage for future experiments to determine the potential of acoustic streaming as a low weight modification to improve compact heat exchangers.
(5930993), Vinith Vijayarajan. "Channel sparsity aware polynomial expansion filters for nonlinear acoustic echo cancellation." Thesis, 2019.
Знайти повний текст джерелаSpeech quality is a demand in voice commanded systems and in telephony. The voice communication system in real time often suffers from audible echoes. In order to cancel echoes, an acoustic echo cancellation system is designed and applied to increase speech quality both subjectively and objectively.
In this research we develop various nonlinear adaptive filters wielding the new channel sparsity-aware recursive least squares (RLS) algorithms using a sequential update. The developed nonlinear adaptive filters using the sparse sequential RLS (S-SEQ-RLS) algorithm apply a discard function to disregard the coefficients which are not significant or close to zero in the weight vector for each channel in order to reduce the computational load and improve the algorithm convergence rate. The channel sparsity-aware algorithm is first derived for nonlinear system modeling or system identification, and then modified for application of echo cancellation. Simulation results demonstrate that by selecting a proper threshold value in the discard function, the proposed nonlinear adaptive filters using the RLS (S-SEQ-RLS) algorithm can achieve the similar performance as the nonlinear filters using the sequential RLS (SEQ-RLS) algorithm in which the channel weight vectors are sequentially updated. Furthermore, the proposed channel sparsity-aware RLS algorithms require a lower computational load in comparison with the non-sequential and non-sparsity algorithms. The computational load for the sparse algorithms can further be reduced by using data-selective strategies.
(9293561), Rih-Teng Wu. "Development and Application of Big Data Analytics and Artificial Intelligence for Structural Health Monitoring and Metamaterial Design." Thesis, 2020.
Знайти повний текст джерелаRecent advances in sensor technologies and data acquisition platforms have led to the era of Big Data. The rapid growth of artificial intelligence (AI), computing power and machine learning (ML) algorithms allow Big Data to be processed within affordable time constraints. This opens abundant opportunities to develop novel and efficient approaches to enhance the sustainability and resilience of Smart Cities. This work, by starting with a review of the state-of-the-art data fusion and ML techniques, focuses on the development of advanced solutions to structural health monitoring (SHM) and metamaterial design and discovery strategies. A deep convolutional neural network (CNN) based approach that is more robust against noisy data is proposed to perform structural response estimation and system identification. To efficiently detect surface defects using mobile devices with limited training data, an approach that incorporates network pruning into transfer learning is introduced for crack and corrosion detection. For metamaterial design, a reinforcement learning (RL) and a neural network based approach are proposed to reduce the computation efforts for the design of periodic and non-periodic metamaterials, respectively. Lastly, a physics-constrained deep auto-encoder (DAE) based approach is proposed to design the geometry of wave scatterers that satisfy user-defined downstream acoustic 2D wave fields. The robustness of the proposed approaches as well as their limitations are demonstrated and discussed through experimental data or/and numerical simulations. A roadmap for future works that may benefit the SHM and material design research communities is presented at the end of this dissertation.