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Full-Text Articles in Mechanical Engineering
Development Of A Muffler Insertion Loss Flow Rig, Jonathan Chen
Development Of A Muffler Insertion Loss Flow Rig, Jonathan Chen
Theses and Dissertations--Mechanical Engineering
Mufflers and silencers are commonly used to attenuate noise sources such as internal combustion engines and HVAC systems. Typically, these environments contain mean flow that can affect the acoustic properties of the muffler components and may produce flow generated noise. To characterize the muffler performance, common metrics such as insertion and transmission loss and noise reduction are used in industry. Though transmission loss without flow is often measured and is a relatively simple bench top experiment and useful for model validation purposes, mean flow can significantly affect the muffler performance. There are a few existing and commercial transmission loss rigs …
A Transfer Matrix Approach To Determine The Low Frequency Insertion Loss Of Enclosures Including Applications, Shujian He
Theses and Dissertations--Mechanical Engineering
Partial enclosures are commonly used to reduce machinery noise. However, it is well known in industry that enclosures sometimes amplify the sound at low frequencies due to strong acoustic resonances compromising the performance. These noise issues are preventable if predicted prior to prototyping and production. Though boundary and finite element approaches can be used to accurately predict partial enclosure insertion loss, modifications to the model require time for remeshing and solving. In this work, partial enclosure performance at low frequencies is simulated using a plane wave transfer matrix approach. Models can be constructed and the effect of design modifications can …
Determination Of Isolator Transfer Matrix And Insertion Loss With Application To Spring Mounts, Shishuo Sun
Determination Of Isolator Transfer Matrix And Insertion Loss With Application To Spring Mounts, Shishuo Sun
Theses and Dissertations--Mechanical Engineering
Transmissibility is the most common metric used for isolator characterization. However, engineers are becoming increasingly concerned about energy transmission through an isolator at high frequencies and how the compliance of the machine and foundation factor into the performance. In this study, the transfer matrix approach for isolator characterization is first reviewed. Two methods are detailed for determining the transfer matrix of an isolator using finite element simulation. This is accomplished by determining either the mobility or impedance matrix for the isolator and then converting to a transfer matrix. One of the more useful metrics to characterize the high frequency performance …
Development And Validation Of Finite Element Approaches To Determine The Insertion Loss Of Louvered Terminations Including Parametric Investigations, Huangxing Chen
Theses and Dissertations--Mechanical Engineering
Louvers are employed at the ends of HVAC ducts to direct airflow, provide weather protection, and attenuate noise. This details two finite element approaches that can be used to assess the acoustic attenuation from a louvered termination. In the first approach, plane wave propagation is assumed inside of a duct with a non-reflective source. On the receiver side, a baffled termination is assumed and the radiation condition is simulated using a non-reflective boundary condition called an automatically matched layer. In the second approach, a short aperture is placed between two infinite acoustic spaces. On the source side, a diffuse acoustic …