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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