A Selection of Dr. Cunefare's Past Research Projects

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Investigation of a Duct End Reflection Loss (ASHRAE, completed 2007)
Active Control of Automotive Disc Brake Squeal (NSF, completed 2006)
Investigations of a Magnetorgheological State-Switched Absorber
Development of the Integrated Acoustics Laboratory, Phases II and III
Investigations into state-switched devices
Structural Acoustic Optimization of Complex Structures
Acoustic emission of trabecular bone
Anechoic chamber qualification (Completed 2003)
Development of the Integrated Acoustics Laboratory, Phase I
Investigations of fastener installation noise (Completed 2000)
Development of a Brake-Squeal Dynamometer (Completed 2000)
Evaluation of criticality alarm system testing (Completed 1998)
Interior noise minimization optimization using FEM/BEM (Completed 1997)
A novel modal model for exterior acoustic radiation (Completed 1997)
 
Investigation of a Duct End Reflection Loss (ASHRAE)
Sponsor: American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE)
Student: Michael Michaud (Graduated 2007)
This project involves the measurement of End Reflection Loss (ERL), the fraction of energy incident on the end of a duct that is reflected back up the duct. The ERL is an important design parameter for predicting HVAC noise levels in occupied spaces, and, is a factor in the determination of the sound power of HVAC air handlers. The project involves the use of the two-microphone impedance tube method to measure the termination impedance for various duct termination configurations, duct sizes, and aspect ratios.
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Active Control of Automotive Disc Brake Squeal (NSF)
Sponsor: The National Science Foundation
Co-PI: Dr. Al Ferri
Students: Jeff Badertscher, Michael Michaux (Graduated 2005)
The objective of this project is to investigate the use of dither control for the suppression of automotive disk brake squeal. A brake dynamometer consisting of a 40 hp speed controlled electrical motor, speed reducer and automotive 'floating' brake caliper system. The dither signal is applied to the system using a piezo-electric stack located in the brake piston. The data acquisition system in place has the ability to measure the braking pressure, brake pad temperature, the normal force on the brake pads, braking torque, in-plane velocity of brake pads and rotor and acoustic measures using a microphone. These parameters will be used to determine the effect of dither control on the effective braking torque and to better understand the system's modal characteristics at the onset of brake squeal. Additional experimental work will address improvements in the actuator control, placement, power supply and control signals.
The National Science Foundation provided funding to conduct more fundamental investigations into the mechanisms for dither suppression of brake squeal. The project involved significant theoretical and modeling activities directed toward developing an improved comprehension of the dynamics involved.
 
Click here for a more detailed description and images related to the experimental portion of this project
 
Click here for a more detailed description and images related to the theoretical portion of this project
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Investigations of a Magnetorgheological State-Switched Absorber
Original Sponsor: Army Research Office and NSF
Participants: Prof. Chris Lynch, Dr. Gregg Larson
Student: Anne-Marie Albanese
This project involves the development of a state-switched vibration absorber (SSA) with a magneto-rheological (MR) silicone gel as a switchable spring element. When a magnetic field is applied across the MR gel, its stiffness properties change, thereby providing the means to switch the stiffness state of the gel. The MR-based SSA considered here was developed to operate at frequencies below 100 Hz, and to be of a size and mass equivalent to classical tuned vibration absorbers (TVA), with a mass of less than 100 g, and with no length dimension larger than 10 cm. SSAs are single-degree-of-freedom mass-spring-damper systems that have a controllably changeable element. Stiffness-switched SSAs, with appropriate control algorithms, have been shown to improve vibration control as compared to classical tuned vibration absorbers, which are comprised of strictly passive elements. An SSA with an appropriate control scheme is advantageous over a TVA because it can attenuate vibration over a much larger bandwidth. The research here focuses on developing an SSA that operates in a low frequency range (<100 Hz), has a small volume, and has a mass on the order of 100 g, and using MR silicone gels as the switchable element.
 
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Development of the Integrated Acoustics Laboratory, Phases II and III
 
Phase II & III: Qualification studies for a semi-anechoic chamber, reverberation room, and associated instrumentation
Sponsor: Ford Motor Company
Status: Completed
Student: Tina Famighettei (Graduated 2005), Patrick Saussus (Graduated, 2003)
As part of a larger grant, The Georgia Institute of Technology received a commitment of $1,080,000 from the Ford Motor Company to construct Phase II and III of the the Integrated Acoustics Laboratory. These phases added a semi-anechoic and a reverberation room and associated instrumentation to the existing resources of the lab. The instrumentation foundation matches that of Phase I, using VXI-based systems. The chambers have been built, and are undergoing qualification.
 
Click here for a more detailed description and images related to the qualification effort for the reverb room.
 
Go to the IAL Home Page.
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Investigations into state-switched devices
Sponsor: Army Research Office
Participants: Prof. Chris Lynch, Dr. Gregg Larson
Student: Mark Holdhusen
A State-Switched Absorber (SSA) is a device capable of instantaneously changing its stiffness, thus it can switch between resonance frequencies, increasing its effective bandwidth as compared to classical tuned vibration absorbers for vibration control. In my masters thesis I considered the experimental performance of the SSA for vibration suppression of an elastically mounted lumped mass base. State switching was achieved using magneto-rheological fluid to connect or disconnect a coil spring in parallel with other coil springs by applying or removing a magnetic field across of the MR fluid. Experiments were performed over a range of forcing and tuning frequencies. The SSA system, optimally tuned, outperformed the optimal classical TVA system for all combinations of forcing frequencies. The thesis also considered the role of damping in the state-switching concept for a simple one-degree of freedom system and for a two-degree of freedom system. Certain values of damping in the system improve performance, while other values hinder the performance of the state-switched absorber, as compared to classical absorbers. In general, a state-switched absorber with optimized tuning and damping is more effective at vibration suppression as compared to a classical vibration absorber with optimized tuning and damping. Currently, I am researching the performance of the state-switched absorber in continuous systems. I am optimizing the performance of the SSA using theoretical models that find the optimal tuning frequencies and location along a continuous beam. Once the theoretical optimization has been determined, an experimental study of the performance of the SSA on continuous beams will be performed. Continuous plates will be considered after the study of beams has concluded.
 
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Structural Acoustic Optimization of Complex Structures
Sponsor: NASA Langley Structural Acoustics Branch, GSRP Program
Student: Wayne Johnson
The tailoring of composite material properties for maximum strength, stiffness, and the like has been addressed quite often in the literature. However, the design of structures for optimal acoustic properties has been limited--and even more so for composite structures. Of the few works addressing structural acoustic optimization of composites, none fully explain how or why certain designs of the properties lead to an improved acoustic environment enclosed by structures such as cylindrical shells. Further, it is unclear as to what mechanisms and design trends control the interior acoustic environment. In light of these uncertainties, this work intends to examine how the design of a laminated composite cylindrical shell can be used to tailor the structural acoustic coupling and acoustic environment of the enclosed acoustic volume. For example, is there some particular set of ply orientation and thus some stiffness distribution of the cylinder leading to lower levels interior noise? Furthermore, what is the best way to characterize the structural acoustic coupling between the cylinder and the enclosed cavity? The approach employed in this study consists of performing structural acoustic optimizations of a composite cylindrical shell subject to external harmonic monopole excitation, and with various ply angle design variable formulations. The results of these analyses will then be interpreted based on the decomposition of the interior acoustic potential energy.
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Acoustic emission of trabecular bone
Participant:Kenneth Cunefare, Robert Guldberg
Student: Gaylon Hollis
Sponsor: Georgia Tech

The objective of this project is to experimentally assess the acoustic emission from trabecualar bone.&nbsp; The project will incorparate a digital signal procressing system with a material testing system to simultaneously acquire acoustic emission&nbsp;and stress/strain data.&nbsp; The trabeculuar bone specimens are cylindrical in shape and&nbsp;extracted from bovine femurs. The motivation for the project is to further develop a non-invasive technique for analyzing and reporting microdamage in trabecular bone.&nbsp; Trabecular bone is the region most&nbsp;affected by osteoporosis.
 
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Anechoic chamber qualification (Completed 2003)
Sponsor: Ford Motor Company
Students: Patrick Saussus
Modern anechoic chambers are designed to simulate free space in a compact environment. The walls, floors, and ceilings are themselves designed to limit the amount of exterior noise entering the chamber. The applications for such chambers are highly varied, ranging from testing loudspeaker directivity to investigations of noise sources on air conditioning equipment. The ability of the chamber to absorb sound is critical to its effectiveness in simulating free space. Current standards, which define the minimum performance characteristics of an anechoic chamber, require that sound emitted within the chamber follows the inverse square law within specified tolerance levels. A crucial assumption is that the sound source act as an omnidirectional monopole. In other words, the source produces identical sound pressure levels at any radial distance, regardless of the direction. These sources can then be used to determine if the chamber can be used to perform free space tests. Each proposed source must comply with the current industry standards on directionality within specified frequency bands.
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Development of the Integrated Acoustics Laboratory, Phase I
 
Phase I: Acquisition of an Anechoic chamber and associated instrumentation
Sponsor: Ford Motor Company, National Science Foundation, Georgia Tech
Participants: Prof.Yves Berthelot and Prof. Krishan Ahuju
Status: Completed
This project will construct and instrument a state of the art anechoic facility on the Georgia Tech campus beginning in 1997. The thrust of the facility is to provide the capability for closely integrated design, modeling and testing for vibration and acoustical considerations. The facility will include a scanning laser vibrometer, systems for acoustic holography and intensity mapping, a VXI data acquisition system incorporating 32 channels of 0-52 kHz sampling, one channel at 20 MHz sampling, 16 channels of D/A, and a four-channel arbitrary source. In addition, the lab will add two workstations. One of the workstations will serve as the VXI front end, while the other will be used for modeling and simulations, using such codes as MSC/NASTRAN, SYSNOISE, AAC COMET/Acoustics, and others.
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Investigations of fastener installation noise (Completed 2000)
Sponsor: Huck International
Participants: Van Biesel
Student: Mark Fowler
The objective of this project is to experimentally determine the noise generation mechanisms associated with the installation process for a particular high-performance fastener.
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Development of a Brake-Squeal Dynamometer (Completed 2000)
Sponsor: Integrated Acoustics Laboratory, Trelleborg, General Motors
Students: Ryan Rye, Aaron Graf
The objective of this project is to develop a brake-squeal dynamometer facility for investigation of brake-squeal phenomena. Additional project details may be found here. The project incorporates a 40 Hp speed-controlled electrical motor, a Polytec scanning laser vibrometer, and an acoustic intensity probe system. Data acquisition and control are performed by LabView through an NI thermocouple card and an 8 channel Microstar Laboratories high-speed data acquisition card.
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Evaluation of criticality alarm system testing (Completed 1998)
Sponsor: ERDA/Westinghouse Savannah River
Research Engineer: Brian Van Biesel
The objective of this research is to investigate the methods and alternatives used to determine the audibility of criticality alarm systems. Included within the scope is the impact the presence of personal protective clothing (hoods, air suits, respirators) has on the ability of the wearer to hear an alarm. The project also includes sound power measurements on a number of portable devices.
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Interior noise minimization optimization using FEM/BEM (Completed 1997)
Sponsor: NASA Langley Structural Acoustics Branch
Students: Brian Dater, Scott Crane
Research Engineer: Brian Van Biesel
The objective of this research is to develop a computational design tool for reducing the interior noise levels within structures, e.g. aircraft fuselages and vehicle cabins. The work integrates the commercial software codes NASTRAN and COMET/Acoustics with a number of purpose-developed translators and processor codes to implement an optimization algorithm. Available optimizers within the algorithm include CONMIN, COMPLEX, Simulated Annealing, and Hooke and Jeeves. Results to date indicate a significant potential to reduce interior noise levels through appropriated optimal design of the structure.
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A novel modal model for exterior acoustic radiation (Completed 1997)
Sponsor: NASA Langley Graduate Student Researchers Program
Student: Mary Noelle Currey
This research examines a modal decomposition technique for exterior acoustic fields. The work is directed toward understanding the limitations and physical interpretation of the method. the technique generates a set of 'acoustic modes' that are uncoupled with respect to the radiation. This is in contrast to structural modes, which exhibit full coupling between all modes. The radiation modes have very simple frequency dependencies, and widely different radiation efficiencies. These characteristics permit the modeling of a structure's radiation through only a limited set of modes, simplifying computation and control efforts.
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