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- Title
- NOISE CONSIDERATIONS IN DIGITAL SYSTEMS.
- Creator
- FENNELL, ROBERT DEWAYNE., Florida Atlantic University, Graham, Peter
- Abstract/Description
-
The use of digital circuits in incre asingly diverse applications and environments has greatly increased the probability of electromagnetic interference in digital machines. The source and control of noise in digital systems have become major considerations in hardware design. This paper addresses these problems and their solutions. The noise immunities of various semiconductor families are compared showing design tradeoffs. The effects of transmission line reflections on digital wave forms...
Show moreThe use of digital circuits in incre asingly diverse applications and environments has greatly increased the probability of electromagnetic interference in digital machines. The source and control of noise in digital systems have become major considerations in hardware design. This paper addresses these problems and their solutions. The noise immunities of various semiconductor families are compared showing design tradeoffs. The effects of transmission line reflections on digital wave forms are analyzed. The means for calculating interference between conductors (crosstalk) are shown with appropriate approximations. The effects of shielding conductors and circuitry are explored with formulas for near field calculations shown. Proper grounding and power supply decoupling methods are shown to be paramount to proper system design. The paper ends with an approximate noise analysis of a simple computing machine.
Show less - Date Issued
- 1978
- PURL
- http://purl.flvc.org/fcla/dt/13915
- Subject Headings
- Noise control, Digital electronics
- Format
- Document (PDF)
- Title
- Analysis of factors affecting the sound generated by airboats.
- Creator
- Perez, Aquiles., Florida Atlantic University, Masory, Oren, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
This study presents an experimental and analytical investigation of the factors that affect the sound generated by airboats as well as the interaction among these factors; an airboat travels on water and wet land by means of an air pusher propeller attached to an internal combustion engine. These analyses show that the engine and propeller RPM are the main contributors of sound. The contribution of the engine is a tonal sound that is reduced by using a muffler. The sound generated by the...
Show moreThis study presents an experimental and analytical investigation of the factors that affect the sound generated by airboats as well as the interaction among these factors; an airboat travels on water and wet land by means of an air pusher propeller attached to an internal combustion engine. These analyses show that the engine and propeller RPM are the main contributors of sound. The contribution of the engine is a tonal sound that is reduced by using a muffler. The sound generated by the propeller is a flapping sound clearly identified at high revolutions (over 1800 RPM). Above mid-range speeds, the propeller sound takes over, and any reduction of sound on the muffler does not play any role. The only method to control the sound of an airboat without any design modifications is to maintain the operational RPM at mid-range when the muffler's devices contribute to the sound reduction.
Show less - Date Issued
- 2006
- PURL
- http://purl.flvc.org/fcla/dt/13347
- Subject Headings
- Internal combustion engines--Noise, Noise control
- Format
- Document (PDF)
- Title
- NOISE PREDICTION METHODS.
- Creator
- Perry, Nicole Kent, Glegg, Stewart, Florida Atlantic University, Department of Ocean and Mechanical Engineering, College of Engineering and Computer Science
- Abstract/Description
-
Noise prediction methods are necessary in aspects of aerodynamic and hydrodynamic engineering. Predictive models of noise from rotating machinery ingesting turbulence is of much interest and relatively recently studied. This thesis presents a numerical method processed in a series of three codes that was written and edited to receive input for geometrical features of rotating machinery, as well as, adjustments to turbulent operating conditions. One objective of this thesis was to create a...
Show moreNoise prediction methods are necessary in aspects of aerodynamic and hydrodynamic engineering. Predictive models of noise from rotating machinery ingesting turbulence is of much interest and relatively recently studied. This thesis presents a numerical method processed in a series of three codes that was written and edited to receive input for geometrical features of rotating machinery, as well as, adjustments to turbulent operating conditions. One objective of this thesis was to create a platform of analysis for any rotor design to obtain five parameters necessary for noise prediction; 1) the hydrodynamic inflow angle to each blade section, 2) chord length as a function of radius, 3) the cylindrical radius of each blade section, 4) & 5) the leading edge as a function of span in both the rotor-plane and as a function of axial distance downstream. Another objective of this thesis was to use computational fluid dynamics (CFD), specifically by using a Reynold’s-Averaged Navier-Stokes (RANS) Shear Stress Transport (SST) 𝑘 − 𝜔 model simulation in ANSYS Fluent, to obtain the turbulent kinetic energy distribution, also necessary in the noise prediction method presented. The purpose of collecting the rotor geometry data and turbulent kinetic energy data was to input the values into the first of the series of codes and run the calculation so that the output spectra could be compared to experimental noise measurements conducted at the Stability Wind Tunnel at Virginia Tech. The comparison shows that the prediction method results in data that can be reliable if careful attention is payed to the input parameters and the length scale used for analysis. The significance of this research is the noise prediction method presented and used simplifies the model of turbulence by using a correlation function that can be determined by a one-dimensional function while also simplifying the iterations completed on rotor blade to calculate the unsteady forces.
Show less - Date Issued
- 2020
- PURL
- http://purl.flvc.org/fau/fd/FA00013487
- Subject Headings
- Noise, Aerodynamic noise, Hydrodynamics, Noise control--Mathematical models
- Format
- Document (PDF)
- Title
- Broadband noise prediction for subsonic prop fans.
- Creator
- Petithomme, Michel-Olivier., Florida Atlantic University, Glegg, Stewart A. L., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Broadband noise generated by subsonic ducted propfans is studied for a hard walled flanged duct with an infinite centerbody and in a uniform flow. The interaction between boundary layers and blades and the impingement of the blade wakes on the stators are the main sources of noise considered in the forward and rear arc respectively. An efficient method of programming is presented which reduces the time of computation of expressions. The results obtained are presented and discussed. The...
Show moreBroadband noise generated by subsonic ducted propfans is studied for a hard walled flanged duct with an infinite centerbody and in a uniform flow. The interaction between boundary layers and blades and the impingement of the blade wakes on the stators are the main sources of noise considered in the forward and rear arc respectively. An efficient method of programming is presented which reduces the time of computation of expressions. The results obtained are presented and discussed. The boundary layer noise is found to have no sufficient energy at low frequencies regarding the available data, unless the boundary layer thickness is increased by a small amount. Finally, good predictions are obtained with the wake noise although some parameters would require a better evaluation.
Show less - Date Issued
- 1993
- PURL
- http://purl.flvc.org/fcla/dt/14925
- Subject Headings
- Fans (Machinery)--Noise, Noise control, Rotors--Noise
- Format
- Document (PDF)
- Title
- IMPULSE NOISE AND ITS EFFECT ON RECEIVING STRUCTURES: A SURVEY AND SIMULATION.
- Creator
- CADD, JIMMY WILLIAM., Florida Atlantic University, Sudhakar, Raghavan
- Abstract/Description
-
The effects of impulse noise on receiving systems are studied and impulse noise models commonly used in analysis of such receiving systems are introduced. Various techniques for identifying the optimum receiving structure are presented and the concept of a nonlinear receiver for enhancing receiver environments is evolved. performance in impulse noise The effect of finite predetection bandwidth on the performance of such nonlinear receiver structures is studied in a qualitative fashion through...
Show moreThe effects of impulse noise on receiving systems are studied and impulse noise models commonly used in analysis of such receiving systems are introduced. Various techniques for identifying the optimum receiving structure are presented and the concept of a nonlinear receiver for enhancing receiver environments is evolved. performance in impulse noise The effect of finite predetection bandwidth on the performance of such nonlinear receiver structures is studied in a qualitative fashion through computer simulation. The performance of a linear receiver (matched filter) is compared to that of nonlinear receiver structures employing nonlinearities such as blanker and softlimiter; noncoherent ASK modulation was used for the computer simulation experiment. The performance of the blanker and softlimiter is then compared for different predetection bandwidths. An attempt was made to optimize a particular receiver structure in terms of the predetection bandwidth, for a given model of corrupting noise parameters (Gauss~an and impulsive).
Show less - Date Issued
- 1986
- PURL
- http://purl.flvc.org/fcla/dt/14318
- Subject Headings
- Signal theory (Telecommunication), Noise control
- Format
- Document (PDF)
- Title
- Broadband blade self noise prediction for subsonic prop fans.
- Creator
- Jochault, Cyrille Andre., Florida Atlantic University, Glegg, Stewart A. L.
- Abstract/Description
-
Broadband self-noise generated by rotating blades in a subsonic ducted propfan is studied for a hard walled cylindrical duct in a uniform flow. An expression for the induct sound power radiated by three self-noise mechanisms is derived: the Turbulent-Boundary-Layer-Trailing-Edge noise, the Laminar-Boundary-Layer-Vortex-Shedding noise and the Trailing-Edge-Bluntness noise. The present theory uses NASA's self-noise prediction methodology for an isolated airfoil. An efficient method of...
Show moreBroadband self-noise generated by rotating blades in a subsonic ducted propfan is studied for a hard walled cylindrical duct in a uniform flow. An expression for the induct sound power radiated by three self-noise mechanisms is derived: the Turbulent-Boundary-Layer-Trailing-Edge noise, the Laminar-Boundary-Layer-Vortex-Shedding noise and the Trailing-Edge-Bluntness noise. The present theory uses NASA's self-noise prediction methodology for an isolated airfoil. An efficient method of programming is presented which reduces the time of computation for multiple radial modes. The results obtained are presented, discussed and compared with Blade-Tip-Boundary-Layer fan noise predictions obtained using the SDPF code developed at FAU. The most important parameters which affect self-noise are found to be the angle of attack, the effective Mach number and the chord length of the blade. For high angles of attack, the TBL-TE noise gives significant amount of sound power especially at the low frequencies. For low effective Mach numbers and at certain angles of attack, the LBL-VS noise can have high power levels in the mid and high frequencies. Trailing edge bluntness noise appeared to give insignificant amounts of energy over the whole spectrum compared to the other self-noise mechanisms.
Show less - Date Issued
- 1996
- PURL
- http://purl.flvc.org/fcla/dt/15255
- Subject Headings
- Blades--Noise, Rotors--Noise, Noise control, Aerofoils--Noise
- Format
- Document (PDF)
- Title
- Design and implementation of an adaptive control system for active noise control.
- Creator
- Duprez, Adrien Eric., Florida Atlantic University, Cuschieri, Joseph M.
- Abstract/Description
-
This thesis describes the design and implementation of an adaptive control system for active noise control. The main approaches available for implementing an active noise controller are presented and discussed. A Least Mean Squares (LMS) based algorithm, the Filtered-X LMS (FXLMS) algorithm, is selected for implementation. The significance of factors, such as delays, system output noise, system complexity, type and size of adaptive filter, frequency bandwidth, etc..., which can limit the...
Show moreThis thesis describes the design and implementation of an adaptive control system for active noise control. The main approaches available for implementing an active noise controller are presented and discussed. A Least Mean Squares (LMS) based algorithm, the Filtered-X LMS (FXLMS) algorithm, is selected for implementation. The significance of factors, such as delays, system output noise, system complexity, type and size of adaptive filter, frequency bandwidth, etc..., which can limit the performance of the adaptive control, is investigated in simulations. For hardware implementation, a floating-point DSP is selected to implement the adaptive controller. The control program and its implementation on the DSP are discussed. The program is first tested with a hardware-in-the-loop set-up and then implemented on a physical system. Active Noise Control in a duct is finally successfully demonstrated. The hardware and the results are discussed.
Show less - Date Issued
- 2001
- PURL
- http://purl.flvc.org/fcla/dt/12771
- Subject Headings
- Adaptive control systems, Active noise and vibration control
- Format
- Document (PDF)
- Title
- Prediction of broadband self-noise of an airfoil.
- Creator
- Gomez, Carlos L., Florida Atlantic University, Glegg, Stewart A. L.
- Abstract/Description
-
With the increase of air traffic and the introduction of larger aircraft and therefore larger engines, the noise generated by aircraft engines have become of greater importance. In order to address these problems, noise prediction codes must be developed in order to better understand the noise generating process. This thesis addresses important issues related to broadband self-noise from ducted fans based on the prediction model developed by Glegg and Jochault [1]. By addressing issues...
Show moreWith the increase of air traffic and the introduction of larger aircraft and therefore larger engines, the noise generated by aircraft engines have become of greater importance. In order to address these problems, noise prediction codes must be developed in order to better understand the noise generating process. This thesis addresses important issues related to broadband self-noise from ducted fans based on the prediction model developed by Glegg and Jochault [1]. By addressing issues regarding the prediction of broadband self-noise from an isolated airfoil with the observer in the far field directly overhead (at 90° above), improvements can be made to Glegg and Jochault's approach for ducted fans. The prediction of broadband self-noise at 90° above a single airfoil is done by considering boundary layer parameters, the results obtained are compared with theoretical approaches, as well as experimental results obtained by Brooks [2] in order to verify its accuracy.
Show less - Date Issued
- 2006
- PURL
- http://purl.flvc.org/fcla/dt/13377
- Subject Headings
- Aerofoils--Noise, Noise control, Blades--Noise, Rotors--Noise, Acoustical engineering--Mathematical models, Acoustic models
- Format
- Document (PDF)
- Title
- Noise radiation from an open grid bridge.
- Creator
- Tournour, Michel Andre., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
When a vehicle crosses the grid section of an open grid or bascule bridge, a tonal noise is generated. The tonal character of the noise is a consequence of the periodic excitation of both the tire and the grid, that comes from the interaction between the vehicle tire and the periodic grid members. In this thesis, the parameters that control the level and frequency of the generated noise are investigated, with emphasis on understanding the contribution to the overall noise level from the...
Show moreWhen a vehicle crosses the grid section of an open grid or bascule bridge, a tonal noise is generated. The tonal character of the noise is a consequence of the periodic excitation of both the tire and the grid, that comes from the interaction between the vehicle tire and the periodic grid members. In this thesis, the parameters that control the level and frequency of the generated noise are investigated, with emphasis on understanding the contribution to the overall noise level from the vibrations of the grid. Field and laboratory measurements have been performed, together with analytical analysis, on sample grid designs. By determining the acoustic radiation efficiency of the grid, the noise contribution from the grid vibrations is estimated by combing the radiation efficiency with the field measured vibration levels. The results of this study show that the contribution from the grid is small compared to that which may be coming from the vibration of the tire. Without first reducing tire noise, structural modifications to the grid in the form of damping or acoustic baffles will not produce any significant noise reduction.
Show less - Date Issued
- 1994
- PURL
- http://purl.flvc.org/fcla/dt/15046
- Subject Headings
- Bridges--Design and construction, Bridges, Steel plate deck, Bridges--Noise, Noise control, Bridges--Vibration
- Format
- Document (PDF)
- Title
- Ensemble-classifier approach to noise elimination: A case study in software quality classification.
- Creator
- Joshi, Vedang H., Florida Atlantic University, Khoshgoftaar, Taghi M., College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
- Abstract/Description
-
This thesis presents a noise handling technique that attempts to improve the quality of training data for classification purposes by eliminating instances that are likely to be noise. Our approach uses twenty five different classification techniques to create an ensemble of classifiers that acts as a noise filter on real-world software measurement datasets. Using a relatively large number of base-level classifiers for the ensemble-classifier filter facilitates in achieving the desired level...
Show moreThis thesis presents a noise handling technique that attempts to improve the quality of training data for classification purposes by eliminating instances that are likely to be noise. Our approach uses twenty five different classification techniques to create an ensemble of classifiers that acts as a noise filter on real-world software measurement datasets. Using a relatively large number of base-level classifiers for the ensemble-classifier filter facilitates in achieving the desired level of noise removal conservativeness with several possible levels of filtering. It also provides a higher degree of confidence in the noise elimination procedure as the results are less likely to get influenced by (possible) inappropriate learning bias of a few algorithms with twenty five base-level classifiers than with a relatively smaller number of base-level classifiers. Empirical case studies of two different high assurance software projects demonstrate the effectiveness of our noise elimination approach by the significant improvement achieved in classification accuracies at various levels of filtering.
Show less - Date Issued
- 2004
- PURL
- http://purl.flvc.org/fcla/dt/13144
- Subject Headings
- Computer interfaces--Software--Quality control, Acoustical engineering, Noise control--Case studies, Expert systems (Computer science), Software documentation
- Format
- Document (PDF)
- Title
- Correcting noisy data and expert analysis of the correction process.
- Creator
- Seiffert, Christopher N., Florida Atlantic University, Khoshgoftaar, Taghi M., College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
- Abstract/Description
-
This thesis expands upon an existing noise cleansing technique, polishing, enabling it to be used in the Software Quality Prediction domain, as well as any other domain where the data contains continuous values, as opposed to categorical data for which the technique was originally designed. The procedure is applied to a real world dataset with real (as opposed to injected) noise as determined by an expert in the domain. This, in combination with expert assessment of the changes made to the...
Show moreThis thesis expands upon an existing noise cleansing technique, polishing, enabling it to be used in the Software Quality Prediction domain, as well as any other domain where the data contains continuous values, as opposed to categorical data for which the technique was originally designed. The procedure is applied to a real world dataset with real (as opposed to injected) noise as determined by an expert in the domain. This, in combination with expert assessment of the changes made to the data, provides not only a more realistic dataset than one in which the noise (or even the entire dataset) is artificial, but also a better understanding of whether the procedure is successful in cleansing the data. Lastly, this thesis provides a more in-depth view of the process than previously available, in that it gives results for different parameters and classifier building techniques. This allows the reader to gain a better understanding of the significance of both model generation and parameter selection.
Show less - Date Issued
- 2005
- PURL
- http://purl.flvc.org/fcla/dt/13223
- Subject Headings
- Computer interfaces--Software--Quality control, Acoustical engineering, Noise control--Computer programs, Expert systems (Computer science), Software documentation
- Format
- Document (PDF)
- Title
- The directionality of noise created by turbulent flow over roughness.
- Creator
- Kaufman, Gerard P., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Flow over a rough surface is known to radiate sound as a dipole source that is directional. In order to better understand this source, measurements are being made in a wind tunnel using a microphone array. The measurements collected by a microphone array are beamformed to give a source image and can be deconvolved with an assumed point spread function in order to obtain the source levels. This thesis considers alternative analysis algorithms that can be used to analyze wind tunnel data. Only...
Show moreFlow over a rough surface is known to radiate sound as a dipole source that is directional. In order to better understand this source, measurements are being made in a wind tunnel using a microphone array. The measurements collected by a microphone array are beamformed to give a source image and can be deconvolved with an assumed point spread function in order to obtain the source levels. This thesis considers alternative analysis algorithms that can be used to analyze wind tunnel data. Only numerical examples of how these algorithms work will be presented and the analysis of real data will be considered in later studies. It will be shown how estimates can be made of the source directivity by comparing the measured data with a theoretical source model and minimizing the error between the model and the measurements.
Show less - Date Issued
- 2011
- PURL
- http://purl.flvc.org/FAU/3171394
- Subject Headings
- Electromagnetic fields, Signal processing, Digital techniques, Noise control, Adaptive signal processing, Acoustic emission, Measurement
- Format
- Document (PDF)
- Title
- Karhunen-Loeve decomposition for non stationary propulsor flow noise.
- Creator
- Kersulec, Jean-Luc., Florida Atlantic University, Glegg, Stewart A. L., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The aim of this thesis is to develop a theory for non stationary propulsor flow noise. The model which is proposed is based on Amiet's paper "Acoustic Radiation from an Airfoil in a Turbulent Stream" [1], which describes broad band noise when a simple model of airfoil interacts with a turbulent flow, under the assumption of stationarity. The Karhunen-Loeve method provides a set of modes which describe the turbulent flow without the assumption of stationarity. A method is described to obtain...
Show moreThe aim of this thesis is to develop a theory for non stationary propulsor flow noise. The model which is proposed is based on Amiet's paper "Acoustic Radiation from an Airfoil in a Turbulent Stream" [1], which describes broad band noise when a simple model of airfoil interacts with a turbulent flow, under the assumption of stationarity. The Karhunen-Loeve method provides a set of modes which describe the turbulent flow without the assumption of stationarity. A method is described to obtain broad band noise calculations when the mean turbulent flow varies with time and produces non stationary turbulence. A comparison of the numerical results obtained with the results from the paper of reference [1] shows the characteristics of time varying sound radiation. The various mathematical formulae will give a starting point to the analysis of real time varying flows, which are not considered in this thesis.
Show less - Date Issued
- 2005
- PURL
- http://purl.flvc.org/fcla/dt/13233
- Subject Headings
- Aerodynamic noise, Turbulence, Aerofoils, Unsteady flow (Aerodynamics), Nonlinear control theory, Differential equations, Nonlinear
- Format
- Document (PDF)
- Title
- Spectral refinement to speech enhancement.
- Creator
- Charoenruengkit, Werayuth., College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
- Abstract/Description
-
The goal of a speech enhancement algorithm is to remove noise and recover the original signal with as little distortion and residual noise as possible. Most successful real-time algorithms thereof have done in the frequency domain where the frequency amplitude of clean speech is estimated per short-time frame of the noisy signal. The state of-the-art short-time spectral amplitude estimator algorithms estimate the clean spectral amplitude in terms of the power spectral density (PSD) function...
Show moreThe goal of a speech enhancement algorithm is to remove noise and recover the original signal with as little distortion and residual noise as possible. Most successful real-time algorithms thereof have done in the frequency domain where the frequency amplitude of clean speech is estimated per short-time frame of the noisy signal. The state of-the-art short-time spectral amplitude estimator algorithms estimate the clean spectral amplitude in terms of the power spectral density (PSD) function of the noisy signal. The PSD has to be computed from a large ensemble of signal realizations. However, in practice, it may only be estimated from a finite-length sample of a single realization of the signal. Estimation errors introduced by these limitations deviate the solution from the optimal. Various spectral estimation techniques, many with added spectral smoothing, have been investigated for decades to reduce the estimation errors. These algorithms do not address significantly issue on quality of speech as perceived by a human. This dissertation presents analysis and techniques that offer spectral refinements toward speech enhancement. We present an analytical framework of the effect of spectral estimate variance on the performance of speech enhancement. We use the variance quality factor (VQF) as a quantitative measure of estimated spectra. We show that reducing the spectral estimator VQF reduces significantly the VQF of the enhanced speech. The Autoregressive Multitaper (ARMT) spectral estimate is proposed as a low VQF spectral estimator for use in speech enhancement algorithms. An innovative method of incorporating a speech production model using multiband excitation is also presented as a technique to emphasize the harmonic components of the glottal speech input., The preconditioning of the noisy estimates by exploiting other avenues of information, such as pitch estimation and the speech production model, effectively increases the localized narrow-band signal-to noise ratio (SNR) of the noisy signal, which is subsequently denoised by the amplitude gain. Combined with voicing structure enhancement, the ARMT spectral estimate delivers enhanced speech with sound clarity desirable to human listeners. The resulting improvements in enhanced speech are observed to be significant with both Objective and Subjective measurement.
Show less - Date Issued
- 2009
- PURL
- http://purl.flvc.org/FAU/186327
- Subject Headings
- Adaptive signal processing, Digital techniques, Spectral theory (Mathematics), Noise control, Fuzzy algorithms, Speech processing systems, Digital techniques
- Format
- Document (PDF)