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Robert, Rene Jean. "Measuring noise level reduction using an artificial noise source." Thesis, Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54480.
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Buildings located near airports may be subjected to significant noise levels due to aircraft flyovers. Aircraft noise is particularly annoying when compared to other traffic noises due to its intermittent nature. While noise control is typically performed at the source, sound insulation programs are in place to improve the acoustic performance of a residence affected by the flyovers. Noise Level Reduction (NLR) is a common metric used in the United States to determine whether a residence qualifies for such programs. Sound insulation programs are available to houses that have an indoor Day Night Average Sound Level (DNL) greater than 45 dBA. NLR is a single-number metric used to quantify the ability for a building or building element to reduce the transmission of external sound pressure levels generated by aircraft. In addition to determining whether a residence qualifies, NLR can be used to quantify the effectiveness of the modifications performed as a result of the sound insulation program. NLR measurements with a loudspeaker offer an alternative method to those performed with aircraft flyovers, offering flexibility to the consultants that perform these measurements in the field. The purpose of this research was to better understand and improve the loudspeaker test for measuring NLR, providing a resource to the aircraft noise industry. Testing was completed on a "test house" that was constructed on campus with construction methods typical of a mixed-humid climate. The angular dependency, repeatability, and reproducibility of NLR, among other factors, were evaluated with field measurements. Significant NLR variations were observed with changes in lateral and vertical angles of incidence.
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Kalyoncu, Ozden. "Noise Reduction In Time-frequency Domain." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608768/index.pdf.
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In this thesis work, time-frequency filtering of nonstationary signals in noise using Wigner-Ville Distribution is investigated. Continuous-time, discrete-time and discrete Wigner Ville Distribution definitions, their relations, and properties are given.
Time-Frequency Peak Filtering Method is presented. The effects of different parameters on the performance of the method are investigated, and the results are presented.
Time-Varying Wiener Filter is presented. Using simulations it is shown that the performance of the filter is good at SNR levels down to -5 dB. It is proposed and shown that the performance of the filter improves by using Support Vector Machines.
The presented time-frequency filtering techniques are applied on test signals and on a real world signal. The results obtained by the two methods and also by classical zero-phase low-pass filtering are compared. It is observed that for low sampling rates Time-Varying Wiener Filter, and for high sampling rates Time-Frequency Peak Filter performs better.
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Su, Hongjiang. "Shoeprint image noise reduction and retrieval." Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486207.
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A shoeprint is a mark made when the sole of a shoe comes into contact with a surfice. People committing crimes inevitably leave their shoe marks at the crime scene. A study suggests that footwear impressions could be located and retrieved at approximately 35% of all crime scenes. More and more shoeprint images have been collected, leading to a few of shoeprint image databases. The constantly increasing of the size of these databases leads to a problem that it takes too much time to classify or retrieve them manually. In addition, when a shoeprint is actually being made, distortion, capture device-dependent noise, and cutting-out can be introduced. This thesis deals with the problems involved in the development of an automated shoeprint image classification/retrieval system. Firstly, it is concerned with investigating the problem of noise and artefact reduction, and the segmentation of a shoeprint from a noisy background. It aims to provide a software package to pre-processing an input shoeprint image from variety of sources. Secondly it is concerned with developing and investigating robust descriptors for a shoeprint image, and it also addresses the problem of matching shoeprint images using these descriptors. In this thesis, some novel techniques for image quality measure, Gaussian noise and Germ-grain noise reduction, pattern segmentation and screening have been developed. In addition, a few of low-level image feature descriptors, pattern & topological spectra and local image features, have been proposed for indexing and searching a shoeprint image dataset. This thesis also has developed a prototype system to demonstrate the proposed algorithms and the application cases in forensic science. Shoeprint image retrieval tests on a few of datasets (totally more than 15, 000 images) suggest that local image features, compared with other shoeprint image descriptors, have great potential to be applied in real-world forensic investigations.
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Bace, Matthew M. (Matthew Mark). "A receiver-compatible noise reduction system." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/116488.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1990.Includes bibliographical references (leaves 111-113).
by Matthew M. Bace.
M.S.
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Read, Simon John. "Noise reduction technologies for open rotors." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608127.
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Haglund, Philip. "Noise reduction solutions for compact dishwasher." Thesis, KTH, Maskinkonstruktion (Inst.), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-157658.
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Electrolux are currently developing a new kind of compact dishwasher, distinctly different from conventional dishwashers. A key concern that emerged through the development process was noise. The sound was characterized as loud and annoying. The goal of this thesis was to develop a mechanical design solution that would guarantee a noise level below 55 dBA. Initial tests reaffirmed the concern regarding noise. Noise was prevalent and the sound pressure level ranging from 58,8 to 59,8 was considered intolerable. Tests were performed in an acoustic lab to determine vibration source and noise factors. The pump was identified as the vibration source and the suspension was identified as the major noise factor. The rubber flange supporting the pump was fastened with screws. Loose screws failed to keep the pump in place whilst tight screws deformed the flange and pushed the pump against an adjacent plastic feature. There was a perceptible increase of 4,5 dBA when the two were in contact, and a palpable increase of 9,4 dBA when they were hitting each other. Metal spacers were the most reliable and effective solution for lowering the noise. Placed between the flange and the screws, the spacers kept the rubber flange from deforming and prevented it from hitting the adjacent feature. Metal spacers reduced the noise level from 60,6 to 51,3 dBA, a difference perceived half as loud. The efficiency of the metal washer was demonstrated in field tests, during which no complaints were made on the noise level. Pumps and dishwashers were tested in a hydraulic lab to determine operating point and best efficiency point. Pump compatibility determines performance and reliability, as poor operating conditions cause additional vibration, noise and wear. Tests concluded that the hydraulic performance and overall efficiency was poor. The operating point ranged from 4 to 8%, far below the best efficiency point of 15%. Pumps were put through a reliability test, none of which met the company requirement for longevity. Conclusions from the research were used to develop a new suspension concept. The design enabled vibrations to be absorbed and ensured infallible assembly. Rubber straps stretch between the pump and three surrounding support rods and provide supported during operation. The elastic suspension counteracts pump motion and dislocation. A prototype was manufactured to demonstrate the principle function and design.Electrolux håller på att utveckla en ny typ av diskbänksdiskmaskin som skiljer sig från konventionella diskmaskiner. Ett problem som framkom under utvecklingsarbetet var ljudnivån som ansågs ovanligt hög och störande. Målet med denna avhandling var att utveckla en mekanisk konstruktionslösning som kunde garanterade en ljudnivå under 55 dBA. Tidiga tester bekräftade problematiken kring ljudnivån. Oljudet var påtagligt och ljudtrycksnivån varierade mellan 58,8 och 59,8 dBa, vilket ansågs oacceptabelt. Tester gjordes i ett akustiskt laboratorium för att fastställa vibrationskällan och ljudsfaktorer. Pumpen identifierades som vibrationskälla och upphängningen identifierades som en viktig ljudsfaktor. Gummiflänsen som höll pumpen på plats fästes med skruvar. Lösa skruvar misslyckades med att hålla pumpen på plats medan åtsittande skruvar deformerade flänsen och tryckte pumpen mot en intilliggande plastdetalj. Ljudet ökade märkbart med 4,5 dBA när de två trycktes mot varandra. När de slogs mot varande blev det en påtaglig ökning med 9,4 dBA. Metalldistanser var den mest tillförlitliga och effektiva lösningen för att dämpa ljudet. De placerades mellan flänsen och skruvarna för att förhindra flänsen från att deformeras och träffa den intilliggande plastdetaljen. Ljudnivån minskade från 60,6 till 51,3 dBA. För en människa upplevs skillnaden som en halvering av ljudnivån. Metalldistansernas effektivitet påvisades i fältprover, där inga klagomål gjordes på ljudnivån. Pumpar och diskmaskiner testades i ett hydrauliklaboratorium för att bestämma driftspunkten och bästa verkningsgradspunkten. Pumpkompatibilitet avgör prestanda och tillförlitlighet, eftersom dåliga driftsförhållanden orsakar ytterligare vibrationer, ljud och slitage. Slutsatsen av testerna var att den hydrauliska prestanda och totala effektiviteten var låg. Driftspunkten varierade från 4 till 8 %, långt under den bästa verkningsgradspunkten kring 15 %. Pumpar sattes på prov i ett tillförlitlighetstest. Ingen av de pumpar som provades uppfyllde kravet på livslängd. En konceptuell pumpupphängning utvecklades baserad på slutsatserna från forskningen. Den var utformades för att absorbera vibrationer och garantera korrekt montering. Pumpen hålls på plats med hjälp av gummiband istället för en gummifläns. Den elastiska upphängningen motverkar pumpens rörelser och förhindrar att den förskjuts. En prototyp tillverkades för att demonstrera konceptets funktion och design.
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Gruber, M. "Airfoil noise reduction by edge treatments." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/349012/.
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The general aim of this thesis is to investigate experimentally airfoil trailing edge noise reduction using various trailing edge geometries. The work presented in this thesis is part of the FP7 European Project FLOCON. This thesis focuses on sawtooth serrations and a detailed study is conducted in which thirty seven sawtooth trailing edges are tested for reducing the noise at various flow velocities and angles of attack. Broadband noise reductions of up to 5 dB are obtained below some critical frequency above which the noise is increased. The mechanisms by which the noise is changed in the presence of sawtooth serrations are also investigated experimentally by measuring the changes introduced in the unsteady surface pressure near the edge, the turbulence in the boundary layer and in the near wake, and also using Howe's model [66] as a reference for comparisons. Generally, it is shown that noise reductions occur due to an attenuation of the interaction between incident and scattered pressures, which results in a decrease of up to a half of the phase speed along the edges compared with the corresponding straight edge. The noise increase is shown to be caused by a cross-flow being forced through the valleys of the serrations by the pressure difference between the two sides of the airfoil near the trailing edge. Four novel trailing edge geometries are also tested to address the high frequency noise increase observed with sawtooth serrations. These are the slits, the sawtooth with holes, the slitted sawtooth and the random trailing edges. The slitted sawtooth are shown to provide a good alternative to sawtooth serrations, and afford similar levels of noise reductions while limiting the high frequency noise increase to no more than 1 dB. Random trailing edges also show reasonable levels of broadband noise reductions of up to 3 dB and no increase at high frequencies. Finally, serrations are used simultaneously at the trailing edge of an upstream airfoil and at the leading edge of a downstream airfoil to reduce trailing edge noise and interaction noise of the airfoils in a tandem configuration. Broadband reductions of up to 8.5 dB are obtained using the slitted sawtooth trailing edge and the leading edge serrations designed by ONERA. It is shown that most of the noise reduction is provided by a reduction of the airfoil leading edge response due to the leading edge serrations, but that sawtooth slitted serrations provide up to about 3.5 dB additional broadband noise reductions due to a reduction in its wake turbulence.
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Kaymak, Erkan. "Noise reduction and active noise control of high frequency narrow band dental drill noise." Thesis, Brunel University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.445923.
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Zheng, Haosheng, and Kaichun Zhang. "Noise Analysis of Computer Chassis and Secondary Sound Source Noise Reduction." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-18547.
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This article focuses on computer noise analysis and noise reduction processing. With the popularity of computers, people are increasingly demanding the comfort of using computers. Solving the noise problem of the computer case can make the working environment more comfortable. People working in a noisy environment for a long time can cause anxiety and the quality of work is not high. The main purpose of this paper is to analyse the characteristics of computer noise and to reduce the noise of the chassis through the secondary sound source. Through the comparison of the experimental and simulation results, the noise reduction effect of the secondary sound source on the computer case is obtained. This paper can provide a scientific reference for the manufacture of computer chassis and improvement of noise.
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Lariviere, Jeffrey P. "Transform-domain echo cancellation and noise reduction." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0016/NQ57614.pdf.
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Nuckolls, William E. "Fan noise reduction from a supersonic inlet." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-08222009-040447/.
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Chan, Henry H. Y. 1977. "Substrate coupling analysis and noise reduction methods." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33960.
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The trend of system-on-a-chip carries on the end of the VLSI era to fulfill the ever-rising demands of electronics industry. As system complexity increases, interconnect becomes the dominant factor over transistor sizes in determining the overall performance. Theoretically, systems-on-a-chip implementations eliminate most packaging interfaces to improve the system-level performance. Manufacturing cost is also reduced by integrating both analog and digital circuits using monolithic CMOS technologies. Unfortunately, substrate coupling is found to be a major obstacle for the advancement of system-on-a-chip. Accurate predictions of substrate coupling in large-scale systems demand a modeling algorithm with high speed and high resolution, which are difficult to achieve simultaneously. This thesis provides a comprehensive approach towards predicting and preventing substrate noise coupling issues in large systems efficiently. We are primarily interested in modeling the epitaxial-type heavily-doped bulk substrate, that is commonly used in system-on-a-chip designs. An efficient substrate parasitics extraction algorithm based on Delaunay triangulation is proposed. It is optimized for large-scale design applications. Active noise suppression circuits that improve guard band noise insulation efficiency are also developed. SPICE simulation results of circuit layouts comprising the proposed substrate model are compared against those with substrate models generated from Cadence AssuraRTM Substrate Coupling Analysis tool. Various experiments are performed to obtain fabrication-related substrate parameters, measure the circuit performance and validate the modeling results.
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O'Sullivan, E. A. "Numerical noise reduction techniques in signal processing." Thesis, Queen's University Belfast, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426583.
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El-Bardisi, Mansour Mohamed Mansour. "Reduction of wind turbine noise through design." Thesis, City University London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332781.
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De, Stefano Antonio. "Wavelet-based reduction of spatial video noise." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342855.
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Hilkhuysen, Gaston. "Effects of noise reduction on speech intelligibility." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0676/document.
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On perçoit souvent la parole en présence de bien d’autres sons. Parfois les interférences sonores atteignent des niveaux tellement élevés que la parole devient inintelligible. Les méthodes de renforcement de la parole tentent de réduire les bruits ambiants, mais on en sait très peu sur l’effet qu’elles produisent sur l’intelligibilité de la parole. Cette thèse explore les effets des méthodes de renforcement de la parole, aussi appelées algorithmes de suppression du bruit, sur la l’intelligibilité.Après une brève introduction sur les notions de renforcement de la parole et d’intelligibilité, on présente trois études qui abordent les effets de ces méthodes d’un point de vue empirique. On démontre que le résultat de la suppression du bruit tend à réduire l’intelligibilité et que cet effet est constant pour une grande variété de niveaux sonores. Quand on fait appel à des experts pour mettre en place un système commercial de suppression du bruit dans le but d’améliorer l’intelligibilité, ils proposent des réglages qui dégradent l’intelligibilité. Les profanes perçoivent bien une amélioration de l’intelligibilité qui résulte des méthodes de renforcement de la parole.Trois autres études subséquentes tentent de préciser les propriétés du signal, qui ont des effets sur l’intelligibilité et qui sont généré par les méthodes de renforcement de la parole. Des métriques physiques basées sur différentes propriétés du signal ont été utilisées pour estimer l’intelligibilité de la parole renforcée. La plupart de ces mesures fournissent des estimations peu fiables ou biaisées de l’intelligibilité absolueSpeech is often perceived in the presence of other sounds. At times the interfering sounds can reach such high levels that the speech becomes unintelligible. Speech enhancement methods attempt to reduce the audibility of noisy sounds, but little is known about how their influence on intelligibility. This thesis explores the effects of speech enhancement, also known as noise suppression algorithms, on speech intelligibility. After a short introduction to speech enhancement and intelligibility, three studies consider the effects from an empirical perspective. It is shown that noise suppression tends to reduce intelligibility and that its effect is mostly constant across a broad range of noise levels. When experts were asked to apply a commercial noise suppressor to optimise intelligibility, they proposed settings that degraded intelligibility. Laypeople successfully identified an increase in intelligibility resulting from speech enhancement. Three subsequent studies attempt to identify the signal properties responsible for the intelligibility effects and generated by speech enhancement.Physical metrics based on various signal properties were used to estimate the intelligibility of the speech-enhanced noisy signal. Most metrics provided unreliable or biased estimates of absolute intelligibility. Some could nevertheless be used to adjust speech enhancers such that intelligibility is optimal
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Depuru, Mohan Nagendra Karthik. "Modelling jet noise reduction : chevrons and microjets." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708351.
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Smith, Corne J. "Feedforward active noise reduction for aircraft headsets." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/49761.
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Thesis (MScEng)--University of Stellenbosch, 2003.ENGLISH ABSTRACT: Active noise reduction (ANR) is a method of cancelling acoustic noise in a defined enclosure. Two methods exist to implement ANR, they are the analog feedback method and the digital feedforward method. Commercial ANR systems employing feedback methods have been around since the 1980's. Feedforward methods have however only become practically implemental with the age of fast real time digital signal processing. In current systems, feedback ANR is used to attenuate broadband noise whilst feedforward methods are used to attenuate narrow band or tonal noise [2]. This thesis investigates feedforward ANR to cancel broadband acoustic noise in aircraft headsets. Different adaptive filters, optimal configuration of adaptive filters and practical limitations to broadband attenuation for headsets are addressed. Results from this thesis show that at least 10dS noise energy attenuation is attainable over a bandwidth of 2.5kHz. A number of areas for further research are also identified.
AFRIKAANSE OPSOMMING: Aktiewe geraas beheer (AGS) is 'n metode om akoestiese geraas te kanselleer in 'n gedefinieerde omgewing. Twee metodes bestaan om AGS te implementeer. Hulle is die analoog terugvoer en digitale vorentoevoer metode. Kommersiële AGS wat die terugvoer metode gebruik is al in gebruik van die 1980's. Vorentoevoer metodes is egter eers sedert vinnige intydse digitale sein prosessering moontlik. In huidige stelsels word terugvoer AGS gebruik vir die attenuasie van wyeband geraas terwyl vorentoevoer metodes gebruik word om nouband of enkel toon geraas te kanselleer [2]. Die tesis ondersoek vorentoevoer AGS om wyeband akoestiese geraas te kanselleer in vliegtuig kopstukke. Verskillende aanpasbare filters, optimale opstelling van aanpasbare filters en praktiese beperkings tot wyeband attenuasie vir kopstukke word ondersoek. Resultate van die tesis wys dat ten minste 10dS geraas energie attenuasie behaal kan word oor 'n bandwydte van 2.5kHz. 'n Aantal areas vir verder navorsing is ook geïdentifiseer.
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Alberts, Antonie Craig. "Phase noise reduction in a multiphase oscillator." Diss., University of Pretoria, 2017. http://hdl.handle.net/2263/66581.
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Oscillators are ubiquitous to radio frequency circuits, where frequency translations and channel selection play a central role in the analogue communications channel. Oscillators also form part of digital systems as a time reference. Typical heterodyne receivers require an intermediate frequency channel. The associated oscillators and variable filters can only be centred perfectly at a single frequency, and degrade performance at the boundaries of the channel. These circuits also require image-rejecting filters and phase-locked loops in order to enable down-conversion. The penalties for these components are increased circuit area and power consumption. A direct down-conversion circuit will reduce the number of components in the system. A requirement added by the structural change is a passive sub-harmonic mixer. Quadrature oscillators may be achieved by cross-coupling two nominally identical LC differential voltage-controlled oscillators. Because of the widespread use of voltage-controlled oscillators in wireless communication systems, the development of comprehensive nonlinear analysis is pertinent in theory and applications. A key characteristic that defines the performance of an oscillator is the phase noise measurement. The voltage-controlled oscillator is also a key component in phase-locked loops, as it contributes to most of the out-of-band phase noise, as well as a significant portion of in-band noise. Current state-of-the-art modulation techniques, implemented at 60 GHz, such as quadrature amplitude modulation, and orthogonal frequency domain multiplexing, require phase noise specifications superior to 90 dBc/Hz at a 1 MHz offset. It has been shown that owing to the timing of the current injection, the Colpitts oscillator tends to outperform other oscillator structures in terms of phase noise performance. The Colpitts oscillator has a major flaw in that the start-up gain must be relatively high in comparison to the cross-coupled oscillator. The oscillation amplitude cannot be extended as in the cross-coupled case. The oscillator’s bias current generally limits the oscillation amplitude. The phase noise is defined by a stochastic differential equation, which can be used to predict the system’s phase noise performance. The characteristics of the oscillator can then be defined using the trajectory. The model projects the noise components of the oscillator onto the trajectory, and then translates the noise into the resulting phase and amplitude shift. The phase noise performance of an oscillator may be improved by altering the shape of the trajectory. The trajectory of the oscillator is separated into slow and fast transients. Improving the shape of the oscillator’s slow manifold may improve its phase noise performance, and improving the loaded quality factor of the tank circuit may be shown to directly improve upon close-in phase noise.
The approach followed describes oscillator behaviour from a circuit-level analysis. The derived equations do not have a closed form solution, but are reformulated using harmonic balance techniques to yield approximate solutions. The results from this closed form approximation are very close to both the numerical solutions of the differential equations, as well as the Simulation Program with Integrated Circuit Emphasis solutions for the same circuits. The derived equations are able to predict the amplitude and frequency in the single-phase example accurately, and are extended to provide a numerical platform for defining the amplitude and frequency of a multiphase oscillator. The analysis identifies various circuit components that influence the oscillator’s phase noise performance. A circuit-level modification is then identified, enabling the decoupling of some of the factors and their interactions. This study demonstrates that the phase noise performance of a Colpitts oscillator may be significantly improved by making the proposed changes to the oscillator. The oscillator’s figure of merit is improved even further. When a given oscillator is set at its optimum phase noise level, the collector current will account for approximately 85% of the phase noise; with the approach in this work, the average collector current is reduced and phase noise performance is improved. The key focus of the work was to identify circuit level changes to an oscillator’s structure that could be improved or changed to achieve better phase noise performance. The objective was not to improve passive components, but rather to identify how the noise-to-phase noise transfer function could be improved. The work successfully determines what can be altered in an oscillator that will yield improved phase noise performance by altering the phase noise transfer function.The concept is introduced on a differential oscillator and then extended to the multiphase oscillator. The impulse sensitivity function of the modified multiphase oscillator is improved by altering the typical feedback structure of the oscillator. The multiphase oscillator in this work is improved from -106 dBc/Hz to -113 dBc/Hz when considering the phase noise contribution from the tank circuits’ bias current alone. This is achieved by uniquely altering the feedback method of the oscillator. This change alters the noise-to-phase noise properties of the oscillator, reducing phase noise. The improvement in the phase noise does not account for further improvements the modification would incorporate in the oscillator’s limit cycle. For a given tank circuit, supply current and voltage, compared to an optimised Colpitts oscillator, the modifications to the feedback structure proposed in this work would further improve the figure of merit by 9 dB. This is not considering the change in the power consumption, which would yield a further improvement in the figure of merit by 7 dB. This is achieved by relaxing the required start-up current of the oscillator and effecting an improvement in the impulse sensitivity function. Future research could include further modelling of the phase shift in the feedback network, including the transmission lines in the feedback networks using the harmonic balance technique in a numerical form. The feedback technique can also be modified to be applicable to single and differential oscillators.
Dissertation (MEng)--University of Pretoria, 2017.
National Research Foundation
The Department of Science and Technology, South Africa
GEW Technologies (Pty) Ltd
Electrical, Electronic and Computer Engineering
MEng
Unrestricted
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Sagoo, Hardial S. "Reduction of noise levels in vaccum cleaners." Thesis, Aston University, 1988. http://publications.aston.ac.uk/15145/.
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The work described in this thesis is directed towards the reduction of noise levels in the Hoover Turbopower upright vacuum cleaner. The experimental work embodies a study of such factors as the application of noise source identification techniques, investigation of the noise generating principles for each major source and evaluation of the noise reducing treatments. It was found that the design of the vacuum cleaner had not been optimised from the standpoint of noise emission. Important factors such as noise `windows', isolation of vibration at the source, panel rattle, resonances and critical speeds had not been considered. Therefore, a number of experimentally validated treatments are proposed. Their noise reduction benefit together with material and tooling costs are presented. The solutions to the noise problems were evaluated on a standard Turbopower and the sound power level of the cleaner was reduced from 87.5 dB(A) to 80.4 db(A) at a cost of 93.6 pence per cleaner. The designers' lack of experience in noise reduction was identified as one of the factors for the low priority given to noise during design of the cleaner. Consequently, the fundamentals of acoustics, principles of noise prediction and absorption and guidelines for good acoustical design were collated into a Handbook and circulated at Hoover plc. Mechanical variations during production of the motor and the cleaner were found to be important. These caused a vast spread in the noise levels of the cleaners. Subsequently, the manufacturing processes were briefly studied to identify their source and recommendations for improvement are made. Noise of a product is quality related and a high level of noise is considered to be a bad feature. This project suggested that the noise level be used constructively both as a test on the production line to identify cleaners above a certain noise level and also to promote the product by `designing' the characteristics of the sound so that the appliance is pleasant to the user. This project showed that good noise control principles should be implemented early in the design stage. As yet there are no mandatory noise limits or noise-labelling requirements for household appliances. However, the literature suggests that noise-labelling is likely in the near future and the requirement will be to display the A-weighted sound power level. However, the `noys' scale of perceived noisiness was found more appropriate to the rating of appliance noise both as it is linear and therefore, a sound level that seems twice as loud is twice the value in noys and also takes into consideration the presence of pure tones, which even in the absence of a high noise level can lead to annoyance.
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Gao, Qiang 1964. "Noise reduction techniques for holographic information storage." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/282620.
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The effects of wavefront conditioning on the performance of holographic optical data storage systems is investigated. The physical origins of various noise mechanisms which degrade the SNR of the holographic storage are studied for the thin phase (DCG) and the photoreflective crystal (LiNbO₃) recording materials. Dependence of the noise on various system parameters such as focal length, pixel size, number of pixels and material parameters are studied. An algorithm is developed to design pseudorandom phase masks which can improve the signal-to-noise ratio for a given system. The noise reduction by using pseudorandom phase mask and a Galilean configuration are investigated theoretically and experimentally. Significant improvement to the signal-to-noise ratio of holographic storage systems is demonstrated experimentally.
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Dang, Dung Do. "Tuneable Diode Laser Absorption Spectroscopy with Optical Fiber : Noise Analysis and Noise Reduction." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2006. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13089.
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A prototype of a fiber based absorptionspectroscopy instrument is built. A single mode fiber pigtailDistributed Feedback laser (DFB) is used to scan a known$mbox{NH}_3$ absorption line near $1512nm$ ($6614cm^{-1}$). $2mm$diameter InGaAs PIN photodiodes are used to convert the light signalto electrical signals by use of special designed transimpedanceamplifiers. Laser modulation, coherent detection at twice themodulation frequency (second harmonic detection), other electronics,and digital signal processing are provided by Norsk Elektrooptikk.bigskip The DFB laser from NEL (NLK1S5EAAA) delivers 10mW fiberoutput and has maximum output around 30mW at maximum injectioncurrent of 200mA. This laser was found to be very quiet at dcoperation. However, in wavelength modulation spectroscopy operationit exhibit large modulation noise that was found to stem from thefiber coupling inside the laser module. A detection limit of$6times10^{-5}$ to $1times10^{-4}$ in absorbance unit with 0.712moptical path length and an effective measurement bandwidth of 52Hzwas achieved by this laser. This is significantly above thedetection limit with free air lasers which achieve $3times10^{-6}$relative absorbance (0.15ppm $mbox{NH}_3$ at room temperature andatmospheric pressure). The acquisition time for each concentrationmeasurement takes 3.2s. Hence, the response time is very fast whichis a common property of wavelength modulation spectroscopy.bigskip The modulation noise problem was attacked by an electronicnoise cancellation scheme. The idea was that since the noise sourceis inside the laser module and no external optical component can beused to reduce it. With great linearity and reliability propertiesof fused biconical taper (FBT) couplers the laser beam is split intotwo identical beams with nearly equal amount of the same noise. Onebeam, signal beam, is used to induce second harmonic signals in thegaseous path. The other beam goes directly to an identicalphotodetector and is used as a reference signal. Two specialdesigned noise canceller circuits were built to remove commonsignals. Both the circuits, based on current subtraction (notoptimized) or voltage subtraction, give comparable results. Themodulation noise was reduced by more than 12dB. A detection limit of$5times10^{-6}$ was achieved with this prototype. Even aftertransmitting the laser beam through a 3200 meter single mode fiber asignal to noise ratio (relative to 100ppm signal) of $180times$.Hence, a sensitivity is $1.1times10^{-5}$ in absorbance unit wasachieved with the basic noise canceller (not optimized). Thiscorresponds to a detection limit of 0.55ppm ammonia (12.5ppm withoutcancellation). The optimized noise canceller could reduce this by afactor of 3 or more.bigskipThe basic noise canceller based on current domain subtraction wasinvestigated in detail and optimized. This new circuit suppressedthe intensity modulation signal by more than 70dB. The 2f noise wasreduced to approximately 50ppb or $1.1times10^{-6}$ in absorbanceunit with an effective noise bandwidth of 52.3Hz and 1m optical pathlength. This is a record sensitivity with such simple electronics.The sensitivity of our fiber based prototype is limited by thefluctuating etalon fringing in the signal beam. Under normaloperation the prototype achieves approximately $pm20$ppb zero pointdrift in the concentration with an acquisition time of 48s (3.5Hznoise bandwidth). By our knowledge these results are the bestavailable and are competitive with the much more complex frequencymodulation spectroscopy technique.bigskipThese balanced transimpedance amplifiers also have the ability tomeasure the absorption spectra directly without modulation.Determining the absorption linewidth and its shape is now a straightforward task. By use of dual beam configuration and noisecancellation thermal effects that caused background fluctuationswere greatly suppressed. The laser delivers high intensity light,$sim22mW$. The dominating noise is the photocurrent shot noise andthe etalon fringing from optical components in the signal path.Remote sensing, in-situ, noninvasive measurements can be performedwith this instrument. In some cases it's flexibility, and remotesensing possibility are of great attractiveness for the industry.The sensitivity is also improved by a factor of two with the fiberbased tuneable diode laser absorption spectroscopy instrument.bigskipIn the end of this thesis we demonstrate the ability to measuremultiple absorption lines simultaneously. The number of measurementpaths is limited by the laser output power.
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Wheeler, Peter David. "Voice communications in the cockpit noise environment : the role of active noise reduction." Thesis, University of Southampton, 1986. https://eprints.soton.ac.uk/52281/.
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This thesis addresses the topic of voice communications in the cockpit noise environment of modern `fast-jet' aircraft and helicopters, and in particular, describes research undertaken in support of the development of a system for reducing the noise level at the operators' ear by acoustic cancellation within the ear defender, known as Active Noise Reduction or ANR. The internal noise spectra of today's high performance `fast-jet' aircraft and military helicopters is described, and the complex interaction of acoustic noise transmission, speech, and microphone noise pick-up, which produces the total acoustic environment at the aircrews' ears, is discussed. Means of mathematically modelling the audio channel, quantifying the components identified above, and identifying areas of shortfall in performance are derived, leading to a procedure for the development of attenuation requirements, described as the communications audit. A model of the electroacoustic characteristics of the ANR ear defender assembly is presented and the sound field distribution within the ear defender/ear cavity, and its effect upon cancellation performance, is discussed. The extensive laboratory and flight testing of the ANR system that has been undertaken is reviewed, paying particular attention to the measurement and analysis techniques employed in such testing. Finally, the performance characteristics of ANR are discussed and compared with the requirements previously established. Design limitations placed upon the system by the constraints of its area of application are described, and the scope for future improvements is considered.
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Meija, J., G. Keidser, Harvey Dillon, Cong-Van Nguyen, and Earl E. Johnson. "The Effect of Linked Bilateral Noise Reduction Processing on Speech in Noise Performance." Digital Commons @ East Tennessee State University, 2011. https://dc.etsu.edu/etsu-works/1962.
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Lee, Jae Seung. "CW and pulsed TWTA phase noise reduction techniques /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2005. http://uclibs.org/PID/11984.
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Backenius, Erik. "Reduction of Substrate Noise in Mixed-Signal Circuits." Doctoral thesis, Linköping : Department of Electrical Engineering, Linköping University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8813.
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Cassidy, M. "Noise Reduction of an Enclosed Diesel Generator Set." Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527667.
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Bunnjaweht, Sawat. "Phase noise reduction techniques for RF signal generator." Thesis, University of Surrey, 2005. http://epubs.surrey.ac.uk/962/.
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Smeatham, David. "The performance of active noise reduction hearing protectors." Thesis, University of Salford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299120.
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Dwyer, Sheila E. (Sheila Elizabeth). "Quantum noise reduction using squeezed states in LIGO." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79427.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Title as it appears in MIT Commencement Exercises program, June 2013: Sensitivity improvement of a LIGO gravitational Wayne detector through squeezed state injection. Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 217-223).
Direct detection of gravitational waves will require earth based detectors to measure strains of the order 10-21, at frequencies of 100 Hz, a sensitivity that has been accomplished with the initial generation of LIGO interferometric gravitational wave detectors. A new generation of detectors currently under construction is designed improve on the sensitivity of the initial detectors by about a factor of 10. The quantum nature of light will limit the sensitivity of these Advanced LIGO interferometers at most frequencies; new approaches to reducing the quantum noise will be needed to improve the sensitivity further. This quantum noise originates from the vacuum fluctuations that enter the unused port of the interferometer and interfere with the laser light. Vacuum fluctuations have the minimum noise allowed by Heisenberg's uncertainty principle, [Delta]X1 [Delta]X2 >/=1, where the two quadratures X1 and X2 are non-commuting observables responsible for the two forms of quantum noise, shot noise and radiation pressure noise. By replacing the vacuum fluctuations entering the interferometer with squeezed states, which have lower noise in one quadrature than the vacuum state, we have reduced the shot noise of a LIGO interferometer. The sensitivity to gravitational waves measured during this experiment represents the best sensitivity achieved to date at frequencies above 200 Hz, and possibly the first time that squeezing has been measured in an interferometer at frequencies below 700 Hz. The possibility that injection of squeezed states could introduce environmental noise couplings that would degrade the crucial but fragile low frequency sensitivity of a LIGO interferometer has been a major concern in planning to implement squeezing as part of baseline interferometer operations. These results demonstrate that squeezing is compatible with the low frequency sensitivity of a full scale gravitational wave interferometer. We also investigated the limits to the level of squeezing observed, including optical losses and fluctuations of the squeezing angle. The lessons learned should allow for responsible planning to implement squeezing in Advanced LIGO, either as an alternative to high power operation or an early upgrade to improve the sensitivity. This thesis is available at DSpace@MIT and has LIGO document number P1300006.
by Sheila E Dwyer.
Ph.D.
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Wettergren, Carl, and Linda Zetterström. "Noise reduction of pedestrian trucks for street unloading." Thesis, KTH, Maskinkonstruktion (Inst.), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-176267.
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This report is the result of a Master’s Degree Thesis done at the Royal Institute of Technology, KTH, during October 2014 to April 2015. The project was commissioned by Lidl in collaboration with Stockholms Stad and Integrated Transport Research Labs at KTH, and is a part of the Off-peak project. The Aim of the project was to help Lidl perform quieter street unloadings during off-peak hours. The unloading, today, is done with electrical pedestrian trucks and roll containers. Information was gathered about the current equipment and the current method of unloading was studied through observations. There were three problematic areas identified: the uneven ground, the hardware and the user. These were studied further on a pedestrian truck which was borrowed from Lidl for the thesis work. A market study was performed to see what solutions existed on the market. Information was also gathered on Off-peak projects in other cities and what the benefits of such projects could be. Study visits were made to Toyota-BT in Mjölby and Karnag in Täby to gather further knowledge. A meeting was held with K.Hartwall at Integrated Transport Research Lab to discuss their current solutions. The three problematic areas were discussed during a midterm meeting. Two of them were selected for future work: an add-on module to keep the fork carriage from rattling and an aid for the drivers of the trucks that shows the noise level. Many iterations of brainstorming, testing and evaluating led to the final results. The testing showed that the module that was supposed to keep the fork carriage from rattling didn’t have the desired results. The choice was then made to develop a spring solution to keep the forks from bouncing of each other. This led to the development of a leaf spring solution that is mounted on the underside of the fork carriage. The development of an aid for the drivers led to the Noise Advisor which is a sound level meter that sits on the side of the trucks mast and gives visual feedback to the driver.Denna rapport är resultatet av ett examensarbete utfört på Kungliga Tekniska Högskolan, KTH, från oktober 2014 till april 2015. Projektets uppdragsgivare var Lidl och det utfördes i samarbete med Stockholms Stad och Integrated Transport Research Labs på KTH, som en del av Off-peak projektet. Målet med projektet var att hjälpa Lidl utföra tystare gatulossningar under off-peak tider. Lossningen idag sker med hjälp av elektriska ledtruckar samt rullburar. En bakgrundsstudie genomfördes där den nuvarande utrustningen och metoden för gatulossning studerades genom observationer på plats. Då identifierades tre problemområden: den ojämna marken, utrusningen och användaren. Dessa studerades vidare på en ledtruck och några rullburar som lånades in från Lidl. En marknadsundersökning utfördes för att se vilka lösningar som redan fanns på marknaden. Andra off-peak projekt i andra städer studerades och vilka fördelar de medförde. Studiebesök gjordes på Toyota-BT i Mjölby och Karnag i Täby för att samla ytterligare kunskap. Ett möte hölls med K.Hartwall på Integrated Transport Research Lab för att diskutera deras nuvarande lösningar. De tre problemområdena diskuterades under ett avstämmningsmöte som hölls i mitten av projektet. Då valdes två av dessa områden: en tilläggsmodul som ska motverka att gaffeln skramlar och en dosa som ger feedback till förare om ljudnivån när hen kör den. Många iterationer av brainstorming, tester och utvärderingar ledde till det slutliga resultatet. Testen visade att påbyggnadsmodulen, som var tänkt att förhindra gaffeln från att skramla, inte gav något bra resultatet. Då gjordes valet att utveckla en lösning som med hjälp av en fjäder förhindrar att gafflarna slår mot varandra. Detta ledde till utvecklingen av en lösning med en bladfjäder som monteras på undersidan av gaffeln. Utvecklingen av ett hjälpmedel till förarna ledde till Noise advisor som är en ljudnivåmätare som sitter på sidan av ledtrucken och ger en visuell feedback till föraren.
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Wang, Yen-Chun, and 王彥鈞. "Hierarchical Noise Reduction." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/59351483167220885106.
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碩士國立臺灣大學
資訊工程學研究所
96
In this thesis, we introduce a hierarchical noise reduction algorithm which can reduce the noise and preserve the details of the images. This hierarchical method converts an image into a set of four downscaled images which contain information of different frequency in original image. Hence we can process the image in different frequency layers without transferring to frequency domain. Afterwards, we find edge pixels in each sub-image and apply different smoothing methods to edge pixels and non-edge pixels. After handling all four layers of original image, four sub-images are combined to produce a de-noised image.
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Wang, Yen-Chun. "Hierarchical Noise Reduction." 2008. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2407200809271000.
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Ho, Ting-Fai, and 何庭輝. "Noise Estimation and Reduction." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/3896zs.
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碩士國立臺北藝術大學
科技藝術研究所碩士班
94
Due to the population of digital image and the broadening usage of digital image data, like interactive installation art, performance art, etc. In order to fulfill the requirements, improving the quality of digital images is very important. In this thesis, we apply a fast monochrome image noise reduction method to color images. We improve the method by adjusting parameters due to different properties of different color space layers. This thesis propose a fast and proper method for color image noise reduction, which is efficient removing Gaussian noise without blurring much image detail.
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Chou, Yu-Te, and 周育德. "Video Signal Noise Reduction." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/17707249836948648249.
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碩士國立雲林科技大學
電機工程技術研究所
88
With the science and technology are more and more progressional, the video plays an important role in human’s daily life. However, how to promote the video quality will become the valued discussion in the modern society. The purpose of this research is mainly aimed at real-time noise reduction system with video signal, based on the noise reduction algorithm and a FPGA chip that was possessed of superior characters, like high-speed operation and reconfiguration, etc. We also will use the hardware description language to plan the exceptional VLSI design. In the end, the noise reduction algorithm circuit is configured into a FPGA chip in order to evaluate the overall video signal noise reduction system.
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Wells, Jered R. "Correlated Polarity Noise Reduction: Development, Analysis, and Application of a Novel Noise Reduction Paradigm." Diss., 2013. http://hdl.handle.net/10161/8246.
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Image noise is a pervasive problem in medical imaging. It is a property endemic to all imaging modalities and one especially familiar in those modalities that employ ionizing radiation. Statistical uncertainty is a major limiting factor in the reduction of ionizing radiation dose; patient exposure must be minimized but high image quality must also be achieved to retain the clinical utility of medical images. One way to achieve the goal of radiation dose reduction is through the use of image post processing with noise reduction algorithms. By acquiring images at lower than normal exposure followed by algorithmic noise reduction, it is possible to restore image noise to near normal levels. However, many denoising algorithms degrade the integrity of other image quality components in the process.
In this dissertation, a new noise reduction algorithm is investigated: Correlated Polarity Noise Reduction (CPNR). CPNR is a novel noise reduction technique that uses a statistical approach to reduce noise variance while maintaining excellent resolution and a "normal" noise appearance. In this work, the algorithm is developed in detail with the introduction of several methods for improving polarity estimation accuracy and maintaining the normality of the residual noise intensity distribution. Several image quality characteristics are assessed in the production of this new algorithm including its effects on residual noise texture, residual noise magnitude distribution, resolution effects, and nonlinear distortion effects. An in-depth review of current linear methods for medical imaging system resolution analysis will be presented along with several newly discovered improvements to existing techniques. This is followed by the presentation of a new paradigm for quantifying the frequency response and distortion properties of nonlinear algorithms. Finally, the new CPNR algorithm is applied to computed tomography (CT) to assess its efficacy as a dose reduction tool in 3-D imaging.
It was found that the CPNR algorithm can be used to reduce x ray dose in projection radiography by a factor of at least two without objectionable degradation of image resolution. This is comparable to other nonlinear image denoising algorithms such as the bilateral filter and wavelet denoising. However, CPNR can accomplish this level of dose reduction with few edge effects and negligible nonlinear distortion of the anatomical signal as evidenced by the newly developed nonlinear assessment paradigm. In application to multi-detector CT, XCAT simulations showed that CPNR can be used to reduce noise variance by 40% with minimal blurring of anatomical structures under a filtered back-projection reconstruction paradigm. When an apodization filter was applied, only 33% noise variance reduction was achieved, but the edge-saving qualities were largely retained. In application to cone-beam CT for daily patient positioning in radiation therapy, up to 49% noise variance reduction was achieved with as little as 1% reduction in the task transfer function measured from reconstructed data at the cutoff frequency.
This work concludes that the CPNR paradigm shows promise as a viable noise reduction tool which can be used to maintain current standards of clinical image quality at almost half of normal radiation exposure This algorithm has favorable resolution and nonlinear distortion properties as measured using a newly developed set of metrics for nonlinear algorithm resolution and distortion assessment. Simulation studies and the initial application of CPNR to cone-beam CT data reveal that CPNR may be used to reduce CT dose by 40%-49% with minimal degradation of image resolution.
Dissertation
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Li, Xiaoli. "Noise reduction for video signals." Thesis, 2002. http://hdl.handle.net/2429/13880.
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Noise reduction is an important aspect of video processing. This thesis proposes
a motion adaptive temporal-spatial noise reduction system. The three-step motion
detection algorithm is the key for the system. First the pixel-to-pixel difference
between two frames are compared to a threshold. This step gives a preliminary
motion detection result for each pixel in the target frame. The preliminary motion
detection results then go through the impulse pattern recognition module, where
some false detections are corrected. The last step of the motion detection method is
the spatial motion detection. It corrects those motion pixels that were mis-detected
as still pixels in previous steps. Therefore, the pixel accurate motion detection
results between the target frame and a reference frame is obtained. These results
are used to control the operations of the temporal filter and the spatial filter. The
temporal average filter only operates on the pixels that is not in motion to avoid
motion artifacts. The edge adaptive spatial filter does little spatial filtering in
the still areas of the picture to maintain the spatial resolution, while does more
aggressive filtering in motion areas of the picture because the human eye is less
sensitive to the blurring of moving objects. Therefore, the maximum noise reduction
effect is achieved.
The proposed algorithm is implemented both in a hardware prototype using
FPGAs and as a real-time software module on a VLIW DSP chip. Both prototypes
made the intensive subjective evaluations of the algorithm possible. It is proved
that the algorithm improves the picture quality about 6 dB, in terms of signal-tonoise
ratio and subjective estimation, for most of the noisy pictures. It introduces
minimum artifacts.
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Gebrekidan, Medhanie Tesfay, Christian Knipfer, and Andreas Bräuer. "Vector casting for noise reduction." 2020. https://tubaf.qucosa.de/id/qucosa%3A71502.
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We report a new method for the reduction of noise from spectra. This method is based on casting vectors from one data point to the following data points of the noisy spectrum. The noise‐reduced spectrum is computed from the casted vectors within a margin that is identified by an envelope‐finder algorithm. We compared here the presented method with the Savitzky–Golay and the wavelet transform approaches for noise reduction using simulated Raman spectra of various signal‐to‐noise ratios between 1 and 25 dB and experimentally acquired Raman spectra. The method presented here performs well compared with the Savitzky–Golay and the wavelets‐based denoising method, especially at small signal‐to‐noise ratios and furthermore relies on a minimum of human input requirements.
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Chen, Chun-Ming, and 陳俊銘. "Hearing aid noise reduction research." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/xqj54e.
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碩士國立澎湖科技大學
電機工程系電資碩士班
106
Hearing impairment severely affects people's communication skills and interpersonal relationships, and it also causes a decline in the quality of life. Hearing aids are the most commonly used devices to improve hearing. However, they are widely available and expensive, and there are some differences in functional performance.The difference in hearing aid quality is judged by its noise status.The main purpose of this paper is how to reduce noise and improve sound quality.
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Chang, Sheng-Yu, and 昌聖喻. "Common Noise Reduction Filter For Active Noise Cancellation Circuit." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/42421308968305601577.
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碩士華梵大學
機電工程研究所
92
In this thesis, a common noise reduction filter topology is used in the feedback control technique to design an active noise cancellation (ANC) circuit for headphone. This new topology has the advantage of reducing the manufacturing cost and improving the air pressure imbalance problem of ANC headphone. Two types of common noise reduction filters, there are 4-amplifiers and 2-amplifiers circuits respectively, are designed in this thesis. From circuit simulation, it found that the center frequency and bandwidth of the 4-amplifiers filter can be tuned easily. However, the 2-amplifier filter has the low cost advantage. Finally, the noise cancellation performance of the proposed ANC headphone is measured with an experimental setup. Comparison between the performance has been made with other commercially available ANC headphones.
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Hung, Sheng-Mao, and 洪勝茂. "Using Active Noise Control Technology in Indoor Noise Reduction." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/03569358478525540523.
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碩士國立臺灣科技大學
電機工程系
90
The traditional approaches to attenuate the undesired noise usually use the sound-absorbing material. However, the passive techniques of noise control application in low-frequency noise canceling may be ineffective when they are relatively costly. In order to overcome these problems, the active noise control system uses the adaptive filter to generate an anti-noise to cancel the primary noise, the anti-noise has equal amplitude and opposite phase with primary noise. If we need large quiet zone in the three-dimensional enclosure, and use the active noise control (ANC) systems based on adaptive filter algorithm, we must configure the arrayed microphone and arrayed loudspeaker, this architecture may be costly, and has more complex secondary effect and feedback effect. So the main objective of this research project is to recommend the small advantage ANC system, it can reduce the cost of hardware and software. We create the conversion time stability method to keep the phase of anti-noise opposite with primary noise. Final, we will present the result of control in real time to reduce the air-filter noise indoor, and the best outcome has 2.7353dB attenuation.
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Luo, Wei-lun, and 羅偉倫. "An adaptive noise reduction system with automatic wind noise detection." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/47500754507193473708.
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碩士國立中央大學
電機工程學系
104
As we have known in our daily life, a great noise on the microphone would be produced and signal-to-noise ratio (SNR) of the perceived speech and its quality would be lowered when wind passes through the microphone. The purpose of this study was to develop an adaptive wind noise reduction system. Our system has two parts: firstly we applied the decision tree machine learning algorithm to detect existence of wind noise with the mel frequency cepstrum coefficients (MFCC) used as input features, and parameters of adaptive filter would be changed to reduce the wind noise. Then we calculated the input short time entropy to detect the voice activity in order to make the output speech signal more comfortable and intelligible. This approach would reduce the wind noise if it detected the input signals with no speech activity. To verify if our system could reduce different wind noise properly, we applied real and simulated wind noise as the noise sources with SNR set from 10 to -10dB, and compared our results with two common noise reduction algorithms: minima controlled recursive averaging (MCRA) and Forward-Backward MCRA (MCRA-FB). Then the objective perceptual evaluation of speech quality (PESQ) approach was used to evaluate the quality of the results. In this study, the MATLAB (The MathWorks, Natick, Massachusetts, USA) program was first used to implement the wind noise reduction system. Our results showed that the PESQ score was increased by 0.35 when compared to the original signal with 0dB SNR real wind noise signal while MCRA-FB algorithm could only increase by 0.05. At the same time, the speech hit rate was 96%, and the accuracy of the wind noise detection rate is 93%. We further implemented the wind noise reduction system on the DSP starter kit (DSK), TMS320C6713 (Texas Instruments, Dallas, Texas, USA) and compared to the results of MCRA. Our results indicated when the line in was used as the signal input, the PESQ score could be increased by 0.25 at high SNR (6dB) signal while the results of MCRA algorithm could not improve the PESQ score. However, when the adaptive directional microphone (ADM) was used as the signal input, the PESQ score of our result was 0.35 higher than that of the original (no noise reduction) system at low SNR (-10dB) signal while the result of MCRA algorithm only improved by 0.2. These results show that our wind noise reduction system could reduce the wind noise properly and achieve better performance than the MCRA algorithm.
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Li, Ming-Hua, and 李明樺. "On Active Noise Control systems with Anti-Noise interference reduction." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/70070974633446314834.
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碩士雲林科技大學
通訊工程研究所碩士班
98
This thesis is focused on the investigation of the acoustic feedback problem that is aroused when an active noise control (ANC) system is trying to eliminate noise. The Filter-X LMS (FXLMS) structure proposed by M.T. Akhtar is modified in such a way that the step size can be adjusted to an optimal value. The improved algorithm, which is named the modified variable step-size FXLMS (MVS FXLMS), has been demonstrated to achieve faster convergence than FXLMS. Moreover, we have found that, even under lower levels of filter design, MVS FXLMS still exhibits some improvement. This feature helps greatly on reducing its hardware cost. Finally, we use a real noise sources to test the feasibility of the system. Simulation results show that the proposed MVS FXLMS algorithm works satisfactorily well.
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Deonarine, Justin. "Noise reduction limits the McGurk Effect." Thesis, 2011. http://hdl.handle.net/10012/6046.
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In the McGurk Effect (McGurk & MacDonald, 1976), a visual depiction of a speaker silently mouthing the syllable [ga]/[ka] is presented concurrently with the auditory input [ba]/[pa], resulting in “fused” [da]/[ta] being heard. Deonarine (2010) found that increasing the intensity (volume) of the auditory input changes the perception of the auditory input from [ga] (at quiet volume levels) to [da], and then to [ba] (at loud volume levels). The present experiments show that reducing both ambient noise (additional frequencies in the environment) and stimulus noise (excess frequencies in the sound wave which accompany the intended auditory signal) prevents the illusory percept. This suggests that noise is crucial to audiovisual integration and that the McGurk effect depends on the existence of auditory ambiguity.
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Liu, Chi-Wei, and 劉志偉. "A Crosstalk-Induced Noise Reduction Method." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/34421914642477752475.
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碩士國立中興大學
資訊科學與工程學系所
99
In the development of manufacture technology, the chip spacing between adjacent wires are also more closer, resulting in coupling between the wires caused by the crosstalk noise interference tends to be severe. The interference of noise often effect signal integrity, it may cause the chip does not have the correct signal, and thus unexpected error occurred. In this paper, we propose an enhanced driver (ED) that having self-tuning ability, and mounted in the interfered wire. The use of small areas of component design, it can save chip area, and can effectively reduce crosstalk noise. ED can be effectively used to optimize the results to reduce energy and power consumption and leakage current consumption. Otherwise ED can reduce the side effect that mounted another component on the wire. It has a concept that spending a small cost, but still can effectively reduce crosstalk noise.
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"A receiver-compatible noise reduction system." Research Laboratory of Electronics, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/4199.
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Matthew M. Bace.Also issued as Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1990.
Includes bibliographical references (p. 111-113).
Supported in part by the National Science Foundation. MIP 87-14969 Supported in part by the Maryland Procurement Office. MDA 904-89-C-3009
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Yen-Lan, Huang. "Noise Reduction Using Enhanced Bilateral Filter." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2106200613590300.
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"Video motion estimation and noise reduction." 2012. http://library.cuhk.edu.hk/record=b5549225.
Full textAbstract:
隨著數碼相機、攝影手機以及監控攝像機的快速普及，每天無數的視頻錄像被創造出來。運動估計是視頻處理中的一種基本問題，這個問題通常被稱為光流估計。現有光流估計算法無法處理發生較大尺度變化的視頻。但尺度變化在視頻和照片中非常普遍，所以尺度不變性的光流估計算法對於其他視頻處理操作諸如圖像去噪算法有很大幫助。所以我們提出新的方法來解決這個問題，以建立兩幀圖像不同尺度像素之間的稠密匹配。我們提出一個新的框架，引入像素級精度的尺度參數，然後提出一種有效的數值計算機制，迭代地優化離散尺度參數和連續光流參數。這個機制顯著地拓展了光流估計在包含各種類型運動的自然場景的實用性。各種攝像設備獲得的視頻都不同程度地遭到噪聲的破壞。雖然已經提出許多視頻去噪算法，但在實際應用中仍然存在許多問題。所以，我們設計一種複雜度很低而且有效的實時視頻去噪算法。我們在視頻去噪的過程中引入高品質的光流估計來校準圖像序列。我們還設計了一種加權平均算法來從之前校準的原始視頻幀中恢復出沒有噪聲的圖像。實驗結果表明相比于其他算法，我們的算法能恢復出更多的細節。更重要的是，我們的算法保證視頻的時域連貫性，對視頻質量來說非常重要。
最後，我們還研究了光照不足的環境下拍攝的視頻和圖像中常見的有色噪聲現象。這種噪聲沒有辦法被現有算法有效地去除，因為它們通常假設噪聲是一個高斯或泊松分佈。根據我們對亮度噪聲和色度噪聲的觀察和分析，我們提出了一種新的去噪方法。我們採用了多分辨率雙重雙邊濾波的方法，借用現有算法去噪的亮度層來引導色度層的去噪。實驗表明，視覺和數據評價都表明了我們算法的有效性。
With the popularity of digital cameras, mobile phone cameras and surveillance systems, numerous video clips are created everyday. Motion estimation is one of the fundamental tasks in video processing. Current optical flow estimation algorithms cannot deal with frames that are with large scale variation. Because scale variation commonly arises in images/videos, a scale invariant optical flow algorithm is important and fundamental for other video operations such as video denoising. In light of this, we propose a new method, aiming to establish dense correspondence between two frames containing pixels in different scales. We contribute a new framework taking pixel-wise scale into consideration in optical flow estimation and propose an effective numerical scheme, which iteratively optimizes discrete scale variables and continuous flow ones. This scheme notably expands the practicality of optical flow in natural scenes containing different types of object movements.
Further, Videos captured by all kinds of sensors are generally contaminated by noise. Although lots of algorithms are published, there are still many problems when applying them to real cases. We design a low-complexity but effective real-time video denoising framework by integrating robust optical flow estimation into the denoising process to register locally frame sequences and designing a weighted averaging algorithm to restore a latent clean frame from a sequence of well registered frames. Experiments show that our algorithm recovers more details than other state-of-the-art video denoising algorithms. More importantly our method preserves temporal coherence, which is vital for videos.
Lastly, we study the chrominance noise which is commonly observed in both videos and images taken under insuficient light conditions. This kind of noise cannot be effectively reduced by state-of-the-art denoising methods under the assumption of a Gaussian or Poisson distributions. Based on the observation of the different characteristics of luminance and chrominance noise, we propose a new denoising strategy that employs multi-resolution dual bilateral filtering on chrominance layers un¬der the guidance of well-estimated luminance layer. Both visual and quantitative evaluation demonstrates the effectiveness of our algorithm.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Dai, Zhenlong.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2012.
Includes bibliographical references (leaves 81-90).
Abstracts also in Chinese.
Abstract --- p.i
Acknowledgement --- p.v
Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Motivation and Objectives --- p.1
Chapter 1.2 --- Our Contributions --- p.6
Chapter 1.3 --- Thesis Outline --- p.8
Chapter 2 --- Background --- p.10
Chapter 2.1 --- Optical Flow Estimation --- p.10
Chapter 2.2 --- Single Image Denoising --- p.15
Chapter 2.3 --- Multi-image and Video Denoising --- p.17
Chapter 3 --- Scale Invariant Optical Flow --- p.20
Chapter 3.1 --- Related Work --- p.23
Chapter 3.2 --- Optical Flow Model with Scale Variables --- p.25
Chapter 3.3 --- Optimization --- p.31
Chapter 3.3.1 --- Computing E[zi] --- p.32
Chapter 3.3.2 --- Minimizing Optical Flow Energy --- p.32
Chapter 3.3.3 --- Overall Computation Framework --- p.34
Chapter 3.4 --- Experiments --- p.37
Chapter 3.4.1 --- Evaluation of Our Model to Handle Scales . --- p.37
Chapter 3.4.2 --- Comparison with Other Optical Flow Methods . --- p.38
Chapter 3.4.3 --- Comparison with Sparse Feature Matching . --- p.43
Chapter 3.4.4 --- Evaluation on the Middlebury Dataset --- p.44
Chapter 3.5 --- Summary --- p.46
Chapter 4 --- Optical Flow Based Video Denoising --- p.47
Chapter 4.1 --- Related Work --- p.48
Chapter 4.2 --- Optical Flow based Video Denoising Framework --- p.48
Chapter 4.2.1 --- Registration --- p.48
Chapter 4.2.2 --- Accumulation --- p.52
Chapter 4.2.3 --- Algorithm Implementation --- p.53
Chapter 4.3 --- Experimental Results --- p.54
Chapter 4.3.1 --- Comparisons with other algorithms --- p.54
Chapter 4.3.2 --- Applications --- p.55
Chapter 4.4 --- Limitation and Future Work --- p.55
Chapter 4.5 --- Summary --- p.59
Chapter 5 --- Chrominance Noise Reduction --- p.62
Chapter 5.1 --- Related work --- p.65
Chapter 5.2 --- Luminance and Chrominance Noise Characteristics --- p.68
Chapter 5.3 --- Luminance and Chrominance Relationship --- p.69
Chapter 5.4 --- Algorithm --- p.71
Chapter 5.4.1 --- Dual Bilateral Filter --- p.71
Chapter 5.4.2 --- Multi-resolution Framework --- p.72
Chapter 5.5 --- Experiments --- p.72
Chapter 5.5.1 --- Quantitative Evaluation --- p.73
Chapter 5.5.2 --- Visual Comparison for Natural Noisy Images --- p.74
Chapter 5.5.3 --- Applications --- p.75
Chapter 5.6 --- Summary --- p.75
Chapter 6 --- Conclusion --- p.79
Bibliography --- p.82
49
李昱辰. "Traffic Noise Reduction at FengAn Areas." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/rfgr49.
Full text
50
Chang-ShengLiou and 劉長陞. "Noise reduction on dynamic system response." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/8db7k7.
Full textAbstract:
碩士國立成功大學
航空太空工程學系
104
This paper proposes a numerical technique to design data filter. The proposed filter is developed for the reduction of additive and data noise contained in the discrete output of implicit continuous dynamics that is modeled by a ration function. However, adding controller will emerge bad effect for any system. So, the merits of this technique include an orders of magnitude reduction in the residual noise level and a negligible induced error on the filtered signal. Reduction in data noise is achieved by smoothing the data sequence. First, we simulate a set of data by computer and filtrate data noise by proposed filter. We investigate which parameter has best performance and which level of noise can be reduced. At last ,we offer envelope function for user.