Mechanical Engineering Commons^™

Sound Absorption Properties Of Functionally Graded Polyurethane Foams, Olivier Doutres Ph.D., Noureddine Atalla Pr.

Olivier Doutres Ph.D.

Noise control over a wide frequency band is an increasingly important design criterion in the building and transport industries. Examples of well known broadband passive concepts for optimal sound absorption are multi-layering with graded properties across the thickness and optimization of the material shape (e.g., wedges). However, for typical applications, the material thickness is limited and shaping or use of different material costly. Thus, there is growing interest for developing acoustical materials having microstructure properties gradient at the micro- or meso-scale; also known as Functionally Graded Materials (FGM). Even if sophisticated models are available to predict the acoustic behavior of …

Resonance Frequencies Of A Spherical Aluminum Shell Subject To Static Internal Pressure, Andrew A. Piacsek, Sami Abdul-Wahid, Robert Taylor

All Faculty Scholarship for the College of the Sciences

Measurements of the vibrational response of a spherical aluminum shell subject to changes in the interior pressure clearly demonstrate that resonance frequencies shift higher as the pressure is increased. The frequency shift appears to be smaller for longitudinal modes than for bending wave modes. The magnitude of frequency shift is comparable to analytical predictions made for thin cylindrical shells. Changes in the amplitudes of resonance peaks are also observed. A possible application of this result is a method for noninvasively monitoring pressure changes inside sealed containers, including intracranial pressure in humans.

Finite Element Modeling And Design Of Honeycomb Sandwich Panels For Acoustic Performance, David Griese

All Theses

Honeycomb cellular metamaterial structures offer many distinct advantages over homogenous materials because their effective material properties depend on both their constituent material properties and their geometric cell configuration. From this, a wide range of targeted effective material properties can be achieved thus supporting forward design by tailoring the honeycomb cellular materials and properties for specific applications. One area that has not been fully explored is the set of acoustic properties of honeycomb materials and how these can offer increased design flexibility when targeting acoustic performance. Understanding these relations, the designer can effectively tune designs to perform better in specific acoustic …

Acoustic Testing And Modeling: An Advanced Undergraduate Laboratory, Daniel A. Russell, Daniel O. Ludwigsen

Physics Publications

This paper describes an advanced laboratory course in acoustics, specifically targeted for students with an interest in engineering applications at a school with a strongly integrated industrial co-op program. The laboratory course is developed around a three-pronged approach to problem solving that combines and integrates theoretical models, computational models, and experimental data. The course is structured around modules that begin with fundamental concepts and build laboratory skills and expand the knowledge base toward a final project. Students keep a detailed laboratory notebook, write research papers in teams, and must pass laboratory certification exams. This paper describes the course layout and …

Dolphin Sound Production And Distribution On The West Florida Shelf, Peter Simard

USF Tampa Graduate Theses and Dissertations

This dissertation is an investigation of dolphin sound production and distribution off west central Florida. Although a wealth of information exists on the production of common sounds (whistles, echolocation) made by captive, trained dolphins, far less is known about free-ranging dolphin sound production and of unusual sounds. In addition, while inshore dolphin populations or communities are the subjects of research projects in many locations, dolphins in offshore waters are less commonly studied. The objectives of this dissertation were to contribute information on free-ranging dolphin sounds and continental shelf dolphin distribution.

While echolocation has been rigorously studied in captive, trained dolphins, …

Simulation Of Whistle Noise Using Computational Fluid Dynamics And Acoustic Finite Element Simulation, Jiawei Liu

Theses and Dissertations--Mechanical Engineering

The prediction of sound generated from fluid flow has always been a difficult subject due to the nonlinearities in the governing equations. However, flow noise can now be simulated with the help of modern computation techniques and super computers. The research presented in this thesis uses the computational fluid dynamics (CFD) and the acoustic finite element method (FEM) in order to simulate the whistle noise caused by vortex shedding. The acoustic results were compared to both analytical solutions and experimental results to better understand the effects of turbulence models, fluid compressibility, and wall boundary meshes on the acoustic frequency response. …