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)
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- 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.
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- Click here for a more detailed description and images
related to the experimental portion of this project
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- 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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- Click here for a more detailed description and images
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- Development of the Integrated Acoustics Laboratory, Phases II and
III
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- 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.
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- Click here
for a more detailed description and images related to the
qualification effort for the reverb room.
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- 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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- Click here
for a more detailed description and images
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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. The project will incorparate
a digital signal procressing system with a material testing system to
simultaneously acquire acoustic emission and stress/strain
data. The trabeculuar bone specimens are cylindrical in
shape and 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.
Trabecular bone is the region most affected by osteoporosis.
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- Click here
for a more detailed description and images
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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.
- Click here for
a more detailed description and images
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- Development of the Integrated
Acoustics Laboratory, Phase I
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- 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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