Rozprawy doktorskie na temat „Noise suppression”
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1
NAKAGAWA, Seiichi, Souta HAMAGUCHI i Norihide KITAOKA. "Noisy Speech Recognition Based on Integration/Selection of Multiple Noise Suppression Methods Using Noise GMMs". Institute of Electronics, Information and Communication Engineers, 2008. http://hdl.handle.net/2237/14965.
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cui, qiaofeng. "Suppression of impulsive noise in wireless communication". Thesis, Högskolan i Gävle, Avdelningen för elektronik, matematik och naturvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-18270.
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This report intends to verify the possibility that the FastICA algorithm could be applied to the GPS system to eliminate the impulsive noise from the receiver end. As the impulsive noise is so unpredictable in its pattern and of great energy level to swallow the signal we need, traditional signal selection methods exhibit no much use in dealing with this problem. Blind Source Separation seems to be a good way to solve this, but most of the other BSS algorithms beside FastICA showed more or less degrees of dependency on the pattern of the noise. In this thesis, the basic mathematic modelling of this advanced algorithm, along with the principles of the commonly used fast independent component analysis (fastICA) based on fixed-point algorithm are discussed. To verify that this method is useful under industrial use environment to remove the impulsive noises from digital BPSK modulated signals, an observation signal mixed with additive impulsive noise is generated and separated by fastICA method. And in the last part of the thesis, the fastICA algorithm is applied to the GPS receiver modeled in the SoftGNSS project and verified to be effective in industrial applications. The results have been analyzed.6
3
Hebert, Robert Carleton University Dissertation Engineering Electrical. "Background acoustic noise suppression in mobile telephony". Ottawa, 1990.
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4
Vilidaite, Greta. "Neural noise and suppression in visual processing". Thesis, University of York, 2017. http://etheses.whiterose.ac.uk/19685/.
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Signal transduction in sensory systems is affected by two major neural mechanisms: neural noise and suppression. Both of these factors present limits on the perceptual abilities of the observer. For example, in contrast discrimination both elevate thresholds. Suppression and neural noise have been implicated in normal sensory development, ageing and several neurological disorders. Of particular interest are autism spectrum conditions (ASCs), in which both neural noise and suppressive mechanisms seem to be atypical. This thesis addresses several issues surrounding the measurement and neural implications of neural noise and suppression. Firstly, it investigates where in the brain neural noise affects sensory processing. Using machine learning algorithms to analyse electro- and magneto-encephalography data, it was found that the main source of neural noise is early sensory cortex. Secondly, it compares psychophysical paradigms used to dissociate the effects of noise and suppression, and suggests refined methods, in particular, using double-pass consistency. Thirdly, it investigates the neural effects of modulating neural noise and suppression selectively using transcranial magnetic stimulation (TMS). It reveals that two existing TMS protocols are suitable for this: single pulses suppress neural signals, whereas triple-pulse TMS increases neural noise. Lastly, the thesis investigates neural noise and gain control (a suppressive mechanism) in ASC. The findings show a relationship between sensory noise and autistic traits in the neurotypical population. Furthermore, electrophysiology data from ASC children and adults as well as a genetic Drosophila model of autism revealed a deficit in the transient dynamics of ASC visual systems, which changes over the course of development. Striking similarities between the fruit fly (Nhe3) model and humans suggests that the genetic model is suitable for further research on ASC sensory symptoms. Taken together, this thesis expands the understanding of neural noise and suppression as well as the situations in which these mechanisms are implicated.
5
Evernham, Jeffrey Thomas. "Acoustic noise suppression for helicopter communication systems". Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/42553.
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Messing, David P. (David Patrick) 1979. "Noise suppression with non-air-acoustic sensors". Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/87444.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.Includes bibliographical references (leaves [74]-[75]).
by David P. Messing.
S.M.
7
Etter, Walter. "Contributions to noise suppression in monophonic speech signals /". [S.l.] : [s.n.], 1993. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10210.
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Rodda, Lasya. "Baseband Noise Suppression in Ofdm Using Kalman Filter". Thesis, University of North Texas, 2012. https://digital.library.unt.edu/ark:/67531/metadc115147/.
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As the technology is advances the reduced size of hardware gives rise to an additive 1/f baseband noise. This additive 1/f noise is a system noise generated due to miniaturization of hardware and affects the lower frequencies. Though 1/f noise does not show much effect in wide band channels because of its nature to affect only certain frequencies, 1/f noise becomes a prominent in OFDM communication systems where narrow band channels are used. in this thesis, I study the effects of 1/f noise on the OFDM systems and implement algorithms for estimation and suppression of the noise using Kalman filter. Suppression of the noise is achieved by subtracting the estimated noise from the received noise. I show that the performance of the system is considerably improved by applying the 1/f noise suppression.
9
Vishal, Kumar. "Incoherent noise suppression and deconvolution using curvelet-domain sparsity". Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/8843.
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Curvelets are a recently introduced transform domain that belongs to a family of multiscale and also multidirectional data expansions. As such, curvelets can be applied to resolution of the issues of complicated seismic wavefronts. We make use of this multiscale, multidirectional and hence sparsifying ability of the curvelet transform to suppress incoherent noise from crustal data where the signal-to-noise ratio is low and to develop an improved deconvolution procedure. Incoherent noise present in seismic reflection data corrupts the quality of the signal and can often lead to misinterpretation. The curvelet domain lends itself particularly well for denoising because coherent seismic energy maps to a relatively small number of significant curvelet coefficients while incoherent energy is spread more or less evenly amongst all curvelet coefficients. Following standard processing of crustal reflection data, we apply our curvelet denoising algorithm to deep reflection data. In terms of enhancing the coherent energy and removing incoherent noise, curvelets perform better than the F-X prediction method. We also use the curvelet transform to exploit the continuity along reflectors for cases in which the assumption of spiky reflectivity may not hold. We show that such type of seismic reflectivity is sparse in the curvelet-domain. This curvelet-domain compression of reflectivity opens new perspectives towards solving classical problems in seismic processing, including the deconvolution problem. We present a formulation that seeks curvelet-domain sparsity for non-spiky reflectivity. Comparing the results with those obtained from sparse spike deconvolution, curvelets perform better than the latter by recovering the frequency components, which get degraded by convolution operator and noise.
10
Zhang, Yang. "Phase noise suppression techniques for 5-6GHZ oscillator design". Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Fall2007/y_zhang_113007.pdf.
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Shou, Xingxian. "The Suppression of Selected Acoustic Noise Frequencies in MRI". Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1281404517.
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Dandu, Sai Venkata Satya Siva Kumar, i Sujit Kadimisetti. "2D SPECTRAL SUBTRACTION FOR NOISE SUPPRESSION IN FINGERPRINT IMAGES". Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13848.
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Human fingerprints are rich in details called the minutiae, which can be used as identification marks for fingerprint verification. To get the details, the fingerprint capturing techniques are to be improved. Since when we the fingerprint is captured, the noise from outside adds to it. The goal of this thesis is to remove the noise present in the fingerprint image. To achieve a good quality fingerprint image, this noise has to be removed or suppressed and here it is done by using an algorithm or technique called ’Spectral Subtraction’, where the algorithm is based on subtraction of estimated noise spectrum from noisy signal spectrum. The performance of the algorithm is assessed by comparing the original fingerprint image and image obtained after spectral subtraction several parameters like PSNR, SSIM and also for different fingerprints on the database. Finally, performance matching was done using NIST matching software, and the obtained results were presented in the form of Receiver Operating Characteristics (ROC)graphs, using MATLAB, and the experimental results were presented.
13
Hung, Chih-Pin. "Signal enhancement based on multivariable adaptive noise cancellation". Thesis, University of the West of Scotland, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294663.
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Ping, Pau Kwok. "Systematic studies on noise control of plastic injection moulding machine". Thesis, University of Warwick, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265624.
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Green, Donald R. "The utility of higher-order statistics in Gaussian noise suppression". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Mar%5FGreen.pdf.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, March 2003.Thesis advisor(s): Charles W. Therrien, Charles W. Granderson. Includes bibliographical references (p. 123). Also available online.
16
Thiemann, Joachim. "Acoustic noise suppression for speech signals using auditory masking effects". Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31073.
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The process of suppressing acoustic noise in audio signals, and speech signals in particular, can be improved by exploiting the masking properties of the human hearing system. These masking properties, where strong sounds make weaker sounds inaudible, are calculated using auditory models. This thesis examines both traditional noise suppression algorithms and ones that incorporate an auditory model to achieve better performance. The different auditory models used by these algorithms are examined. A novel approach, based on a method to remove a specific type of noise from audio signals, is presented using a standardized auditory model. The proposed method is evaluated with respect to other noise suppression methods in the problem of speech enhancement. It is shown that this method performs well in suppressing noise in telephone-bandwidth speech, even at low Signal-to-Noise Ratios.
17
Petrovic, Denis [Verfasser]. "Phase Noise in OFDM : Characterisation, Estimation and Suppression / Denis Petrovic". Aachen : Shaker, 2005. http://d-nb.info/1186589124/34.
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Zou, Yuexian, i 鄒月嫻. "Robust statistics based adaptive filtering algorithms for impulsive noise suppression". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B22823736.
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(Uncorrected OCR)
Abstract
Abstract of thesis entitled
Robust Statistics Based Adaptive Filtering Algorithms
For Impulsive Noise Suppression
Submitted by Yuexian Zou
for the degree of Doctor of Philosophy at The University of Hong Kong in May 2000
The behavior of an adaptive filter is inherently decided by how its estimation error and the cost function are formulated under certain assumption of the involving signal statistics. This dissertation is concerned with the development of robust adaptive filtering in an impulsive noise environment based on the linear transversal filter (LTF) and the lattice-ladder filer (LLF) structures. Combining the linear adaptive filtering theory and robust statistics estimation techniques, two new cost functions, called the mean M -estimate error (MME) and the sum of weighted M -estimate error (SWME), are proposed. They can be taken as the generalizations of the well-known mean squared error (MSE) and the sum of weighted squares error (SWSE) cost functions when the
involving signals are Gaussian.
Based on the SWME cost function, the resulting optimal weight vector is governed by an M-estimate normal equation and a recursive least M -estimate (RLM) algorithm is derived. The RLM algorithm preserves the fast initial convergence, lower steady-state 11
Abstract
derived. The RLM algorithm preserves the fast initial convergence, lower steady-state error and the robustness to the sudden system change of the recursive least squares (RLS) algorithm under Gaussian noise alone. Meanwhile, it has the ability to suppress impulse noise both in the desired and input signals. In addition, using the MME cost function, stochastic gradient based adaptive algorithms, named the least mean Mestimate (LMM) and its transform dOlnain version, the transform domain least mean Mestimate (TLMM) algorithms have been developed. The LMM and TLMM algorithms can be taken as the generalizations of the least-mean square (LMS) and transform domain normalized LMS (TLMS) algorithms, respectively. These two robust algorithms give similar performance as the LMS and TLMS algorithms under Gaussian noise alone and are able to suppress impulse noise appearing in the desired and input signals. It is noted that the performance and the computational complexity of the RLM, LMM and TLMM algorithms have a close relationship with the estimate of the threshold parameters for the M-estimate functions. A robust and effective recursive method has been suggested in this dissertation to estimate the variance of the estimation error and the required threshold parameters with certain confidence to suppress the impulsive noise. The mean and mean square convergence performances of the RLM and the LMM algorithms are evaluated, respectively, when the impulse noise is assumed to be contaminated Gaussian distribution.
Motivated by the desirable features of the lattice-ladder filter, a new robust adaptive gradient lattice-ladder filtering algorithm is developed by minimizing an MME cost function together with an embedded robust impulse suppressing process, especially for impulses appearing in the filter input. The resultant robust gradient lattice-robust
111
Abstract
normalized LMS (RGAL-RNLMS) algorithm perfonns comparably to the conventional GAL-NLMS algorithm under Gaussian noise alone; meanwhile, it has the capability of suppressing the adverse effects due to impulses in the input and the desired signals. The additional computational complexity compared to the GAL-NLMS algorithm is of
O(Nw log Nw) + O(NfI log N,J .
Extensive computer simulation studies are undertaken to evaluate the performance of the RLM, LMM, TLMM and the RGAL-RNLMS algorithms under the additive noise with either a contaminated Gaussian distribution or the symmetric alpha-stable (SaS ) distributions. The results substantiate the analysis and demonstrate the effectiveness and robustness of the developed robust adaptive filtering algorithms in suppressing impulsive noise both in the input and the desired signals of the adaptive filter. In conclusion, the proposed approaches in this dissertation present an attempt for developing robust adaptive filtering algorithms in impulsive noise environments and can be viewed as an extension of the linear adaptive filter theory. They may become reasonable and effective tools to solve adaptive filtering problems in a non-Gaussian environment in practice.
IVabstract
toc
Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy
19
Zou, Yuexian. "Robust statistics based adaptive filtering algorithms for impulsive noise suppression". Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B22823736.
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Ye, Sheng. "Phase realignment and phase noise suppression in PLLs and DLLs /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2003. http://wwwlib.umi.com/cr/ucsd/fullcit?p3091345.
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Wu, Qing, i Lu-yu Yang. "Analysis and Suppression of Power Supply Noise for Airborne Telemetering Transmitter". International Foundation for Telemetering, 2009. http://hdl.handle.net/10150/606023.
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ITC/USA 2009 Conference Proceedings / The Forty-Fifth Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2009 / Riviera Hotel & Convention Center, Las Vegas, NevadaDuring the program researching on airborne telemetering transmitter of a certain remote telemetry system, small size and a variety of voltage on board are design difficulties. Due to the above important factors, the performance of power supply makes a big affect to the parameters of BPSK modulated signal, especially the EVM (Error Vector Magnitude). The author analyzes the cause of power supply noise and puts forward some suggestions to damp the noise. With these methods, the EVM of modulated signal is improved. Finally, we can conclude the related principles about the suppression of power supply noise.
22
Demiroglu, Cenk. "Multisensor Segmentation-based Noise Suppression for Intelligibility Improvement in MELP Coders". Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10455.
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This thesis investigates the use of an auxiliary sensor, the GEMS device, for improving the quality of noisy speech and designing noise preprocessors to MELP speech coders. Use of auxiliary sensors for noise-robust
ASR applications is also investigated to develop speech enhancement algorithms that use acoustic-phonetic
properties of the speech signal.
A Bayesian risk minimization framework is developed that can incorporate the acoustic-phonetic properties
of speech sounds and knowledge of human auditory perception into the speech enhancement framework. Two noise suppression
systems are presented using the ideas developed in the mathematical framework. In the first system, an aharmonic
comb filter is proposed for voiced speech where low-energy frequencies are severely suppressed while
high-energy frequencies are suppressed mildly. The proposed
system outperformed an MMSE estimator in subjective listening tests and DRT intelligibility test for MELP-coded noisy speech.
The effect of aharmonic
comb filtering on the linear predictive coding (LPC) parameters is analyzed using a missing data approach.
Suppressing the low-energy frequencies without any modification of the high-energy frequencies is shown to
improve the LPC spectrum using the Itakura-Saito distance measure.
The second system combines the aharmonic comb filter with the acoustic-phonetic properties of speech
to improve the intelligibility of the MELP-coded noisy speech.
Noisy speech signal is segmented into broad level sound classes using a multi-sensor automatic
segmentation/classification tool, and each sound class is enhanced differently based on its
acoustic-phonetic properties. The proposed system is shown to outperform both the MELPe noise preprocessor
and the aharmonic comb filter in intelligibility tests when used in concatenation with the MELP coder.
Since the second noise suppression system uses an automatic segmentation/classification algorithm, exploiting the GEMS signal in an automatic
segmentation/classification task is also addressed using an ASR
approach. Current ASR engines can segment and classify speech utterances
in a single pass; however, they are sensitive to ambient noise.
Features that are extracted from the GEMS signal can be fused with the noisy MFCC features
to improve the noise-robustness of the ASR system. In the first phase, a voicing
feature is extracted from the clean speech signal and fused with the MFCC features.
The actual GEMS signal could not be used in this phase because of insufficient sensor data to train the ASR system.
Tests are done using the Aurora2 noisy digits database. The speech-based voicing
feature is found to be effective at around 10 dB but, below 10 dB, the effectiveness rapidly drops with decreasing SNR
because of the severe distortions in the speech-based features at these SNRs. Hence, a novel system is proposed that treats the
MFCC features in a speech frame as missing data if the global SNR is below 10 dB and the speech frame is
unvoiced. If the global SNR is above 10 dB of the speech frame is voiced, both MFCC features and voicing feature are used. The proposed
system is shown to outperform some of the popular noise-robust techniques at all SNRs.
In the second phase, a new isolated monosyllable database is prepared that contains both speech and GEMS data. ASR experiments conducted
for clean speech showed that the GEMS-based feature, when fused with the MFCC features, decreases the performance.
The reason for this unexpected result is found to be partly related to some of the GEMS data that is severely noisy.
The non-acoustic sensor noise exists in all GEMS data but the severe noise happens rarely. A missing
data technique is proposed to alleviate the effects of severely noisy sensor data. The GEMS-based feature is treated as missing data
when it is detected to be severely noisy. The combined features are shown to outperform the MFCC features for clean
speech when the missing data technique is applied.
23
Hu, Rongqiang. "Multi-Sensor Noise Suppression and Bandwidth Extension for Enhancement of Speech". Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10452.
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Speech enhancement has been an active research problem for decades and continues to be an important problem. This is made even more true by the proliferation of portable devices having audio input capabilities. In the presence of noise, both the quality and intelligibility of speech signals have been significantly deteriorated.
The proposed research are the frameworks for improving the quality/intelligibility of the degraded speech:
1) a single-channel noise suppression system based on perceptual speech detection
2) multi-sensor noise suppression system for acoustic harsh environments based on non-air conductive sensors
3) a speech bandwidth extension system for telephone speech
Significant improvement in both speech intelligibility and quality from the proposed frameworks are indicated from extensive experiments, inlcuding MOS, DRT, speech recognition task, and log spectral distortion.
24
Hunter-Jones, Nicholas R. "Novel approaches to Newtonian noise suppression in interferometric gravitational wave detection". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/65529.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 63-65).
The Laser Interferometer Gravitational-wave Observatory (LIGO) attempts to detect ripples in the curvature of spacetime using two large scale interferometers. These detectors are several kilometer long Michelson interferometers with Fabry-Perot cavities between two silica test masses in each arm. Given Earth's proximity to various astrophysical phenomena LIGO must be sensitive to relative displacements of 1018 m and thus requires multiple levels of noise reduction to ensure the isolation of the interferometer components from numerous sources of noise. A substantial contributor to the Advanced LIGO noise in the 1-10 Hz range is Newtonian (or gravity gradient) noise which arises from local fluctuations in the Earth's gravitational field. Density fluctuations from seismic activity as well as acoustic and turbulent phenomenon in the Earth's atmosphere both contribute to slight variations in the local value of g. Given the direct coupling of gravitational fields to mass the LIGO test masses cannot be shielded from this noise. In an attempt to characterize and reduce Newtonian noise in interferometric gravitational wave detectors we investigate seismic and atmospheric contributions to the noise and consider the effect of submerging a gravitational wave detector.
by Nicholas R. Hunter-Jones.
S.B.
25
Ling, Matthew K. "Structure and design optimisation of composites for noise suppression in vehicles". Thesis, Sheffield Hallam University, 1992. http://shura.shu.ac.uk/19964/.
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Multi-layered noise control systems are used worldwide in the automotive industry to control vehicles interior noise quality. These composites, which include moulded, and slabstock, polyurethane foam cored carpet systems, are intended to attenuate the ingress of airborne noise and suppress the radiation of structure-borne noise. However, little information has been published on their performance characteristics and the optimisation of their design. This thesis reviews previous theoretical work on the dynamics of panel vibration and the airborne acoustic insulation and the structure-borne isolation provided by composite systems. Mathematical models are developed for the acoustic behaviour of unbonded multilayer foam cored carpet composites as experienced on the experimental test rig. The models identify the important material and system parameters governing behaviour. These models, together with experimental evidence are used to optimise the design of the polyurethane foam core and rank the foam materials in order of performance. The experimental and theoretical studies are not intended for vehicle interior noise prediction purposes. The experimental facility uses a horizontal steel test panel, 1mm thick, about lmxlm, and provides acoustic and vibration excitation. Data are obtained for the effective damping (loss factor) of the 4C panel and the insertion loss (IL) of foam cored composites for both vibration and airborne excitation. The intensity method was used to measure the transmitted noise. The precision of the insertion loss measurements was shown to be better than 1.7dB for frequencies below 4kHz. For airborne excitation reproducibility was better than 1.5dB (f < 2kHz). For vibration excitation the reproducibility was less. This was attributed to the coupling method used. Experimental and theoretical studies are divided into three sections: (i) loss factors, (ii) vibration insertion loss and (iii) airborne insertion loss. Particular attention is given to airborne insertion loss since the precision of measurement allows a detailed analysis to be made. It is shown that IL passes through a minimum governed primarily by the modulus and thickness of the foam core and the surface density of the septum and steel substrate. The level of the IL depends in a complex way on material and design parameters, including the damping of the foam core. The damping of the septum mass is shown to have little effect upon behaviour. The design optimisation procedure described in the thesis takes account of the loudness of vehicle interior noise at relatively high frequencies (f > 500Hz) and the annoyance of discrete tonal noise at relatively low frequencies. It is shown that for a particular incident noise spectrum the carpet composite can be designed to provide the most acceptable noise quality in a vehicle. For a typical large volume production vehicle the optimum resonance frequency is predicted to be about 300Hz. Ways of achieving this frequency with different combinations of design parameters are described.
26
McCoy, Anoma Dayawansa. "Intensity noise suppression using a semiconductor optical amplifier : characterisations and applications". Thesis, University of Southampton, 2005. https://eprints.soton.ac.uk/65501/.
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In this thesis I present a comprehensive system-level study of the intensity noise suppression offered by a saturated semiconductor optical amplifier (SOA), and its application to high channel count spectrum-sliced and optical code division multiplexed (OCDMA) systems incorporating low-cost incoherent light sources. Preliminary investigations into incorporating a saturated SOA to reduce low frequency noise of a highly coherent fibre distributed feedback laser are also presented.
27
Badenhorst, Scott James. "Acceleration of the noise suppression component of the DUCHAMP source-finder". Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/15507.
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The next-generation of radio interferometer arrays - the proposed Square Kilometre Array (SKA) and its precursor instruments, The Karoo Array Telescope (MeerKAT) and Australian Square Kilometre Path finder (ASKAP) - will produce radio observation survey data orders of magnitude larger than current sizes. The sheer size of the imaged data produced necessitates fully automated solutions to accurately locate and produce useful scientific data for radio sources which are (for the most part) partially hidden within inherently noisy radio observations (source extraction). Automated extraction solutions exist but are computationally expensive and do not yet scale to the performance required to process large data in practical time-frames. The DUCHAMP software package is one of the most accurate source extraction packages for general (source shape unknown) source finding. DUCHAMP's accuracy is primarily facilitated by the à trous wavelet reconstruction algorithm, a multi-scale smoothing algorithm which suppresses erratic observation noise. This algorithm is the most computationally expensive and memory intensive within DUCHAMP and consequently improvements to it greatly improve overall DUCHAMP performance. We present a high performance, multithreaded implementation of the à trous algorithm with a focus on 'desktop' computing hardware to enable standard researchers to do their own accelerated searches. Our solution consists of three main areas of improvement: single-core optimisation, multi-core parallelism and the efficient out-of-core computation of large data sets with memory management libraries. Efficient out-of-core computation (data partially stored on disk when primary memory resources are exceeded) of the à trous algorithm accounts for 'desktop' computing's limited fast memory resources by mitigating the performance bottleneck associated with frequent secondary storage access. Although this work focuses on 'desktop' hardware, the majority of the improvements developed are general enough to be used within other high performance computing models. Single-core optimisations improved algorithm accuracy by reducing rounding error and achieved a 4X serial performance increase which scales with the filter size used during reconstruction. Multithreading on a quad-core CPU further increased performance of the filtering operations within reconstruction to 22X (performance scaling approximately linear with increased CPU cores) and achieved 13X performance increase overall. All evaluated out-of-core memory management libraries performed poorly with parallelism. Single-threaded memory management partially mitigated the slow disk access bottleneck and achieved a 3.6X increase (uniform for all tested large data sets) for filtering operations and a 1.5X increase overall. Faster secondary storage solutions such as Solid State Drives or RAID arrays are required to process large survey data on 'desktop' hardware in practical time-frames.
28
Rundström, Per. "Thermal Properties of a 5G Telecom Equipment Casing Design for Noise Suppression". Thesis, KTH, Skolan för industriell teknik och management (ITM), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-299742.
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Around the world the implementation of the 5G mobile network is under way. With this latest generation of mobile data transfer comes many advantages compared to the previous generations. One tradeoff however is the reduced range of the transmitting radios due to the higher frequencies of the signal. One way to solve this is to place smaller radios closer to where the user is. This work studies one such radio and since it is cooled by fans and meant to be placed close to where people live and reside it is favorable to be able to reduce the noise transmitted to its surrounding. This work has therefor developed a proof of concept for a noise suppressing casing that accommodates three radios in order to reduce the total A-weighted sound power level that reaches its surrounding. This was done by using ducts with micro-perforated plates (MPPs) as a sound dampening element. To assist in the design process as well as to verify that placing the radios inside the casing did not raise the temperature of the radio’s component beyond acceptable levels a CFD-simulation was performed. The results of the CFD-simulations were also verified using an experiment where the radio’s temperature was recorded during different fan speeds. When measured, the casing lowered the total A-weighted sound power level of three radios by between 11.6 dB(A) and 14.2 dB(A) depending on the fan speed. The result of the thermal experiment show that the temperature was raised by between 2.8 °C and 5.9 °C depending on the fan speed, with higher fan speeds showing less difference when compared to the radio’s standalone performance. The results are deemed to show promise for the future use of casings fitted with Micro-perforated plates being used to reduce the noise transmitted by telecom radios.Runt om i världen pågår implementeringen av 5G-mobilnätet. Med den senaste generationens mobila dataöverföring kommer många nya fördelar jämfört med tidigare generationer. En nackdel är däremot den kortare räckvidden hos signalen på grund av den högre frekvens som sänds ut av radion. Ett sätt att kringgå detta är att placera mindre radior närmare där användaren befinner sig. Detta examensarbete utgår från en sådan radio och eftersom den kyls med fläktar och ska placeras nära där människor bor och vistas är det fördelaktigt att kunna sänka ljudet som når omgivningen. Därför har ett ljudisolerande hölje utvecklats med plats för tre telekomradior med syfte att sänka den totala A-vägda ljudeffektnivån som når dess omgivning. För att åstadkomma detta användes kanaler i kombination med mikroperforerade plåtar (MPPs) tillsammans som ett ljuddämpande element. Som ett verktyg i designprocessen och för att säkerställa att radions komponenter inte blev för varma gjordes en CFD-simulering. Resultatet av simuleringen verifierades även med ett experiment där temperaturen hos radions kylflänsar mättes under olika fläktvarvtal. När den totala A-vägda ljudeffektnivån mättes för höljet tillsammans med tre radior uppstod en sänkning med mellan 11,6 dB(A) och 14,2 dB(A) beroende på aktuellt fläktvarvtal. Resultatet från experimentet visade även att temperaturen på radions kylfläns höjdes med mellan 2,8 och 5,9 °C beroende på fläktvarvtal, med mindre skillnad för högre fläktvarvtal vid jämförelse med radions temperatur vid drift utan hölje. Resultaten anses visa på den goda potentialen av att använda höljen utrustade med mikroperforerade plåtar för att minska överfört ljud från telekomradior.
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Andersson, David. "Acoustic properties of a 5G Telecom Equipment Shroud Design for Noise suppression". Thesis, KTH, Marcus Wallenberg Laboratoriet MWL, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-302267.
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As technology moves forward it has a tendency to consume more and more power that needs to be cooled by bigger and louder fans, this is especially true for the new generation of 5G radio equipment. This Master thesis is a collaboration with Ericsson and attempts to construct a shroud for containing a number of 5G radio units whilst attenuating the fan noise of the units as effectively as possible. In this project are air ducts used and at the ends silencers are created utilizing the Cremer impedance; the optimal wall impedance for damping an acoustic mode of a propagating wave. To predict the result, a simplified model in an acoustic FEM program was also explored and compared to the sound level of the constructed shroud. The finished shroud successfully reduces the noise of the radio units by 13 dB(A) while causing an increase in temperature of between 2.8°C to 5.9°C. This result was deemed to be a success and the Cremer impedance approach of reducing noise is therefore advised for future development.Allt eftersom tekniken går framåt tenderar den att också förbruka mer och mer energi som i sin tur måste kylas av kraftigare och mer högljudda fläktar, detta fenomen är särskilt påtagligt när det kommer till den senaste generationens radioutrustning för 5G. Detta examensarbete är ett samarbete mellan KTH och Ericsson med avsikt att skapa en kåpa som är designad för att innesluta ett bestämt antal 5G radiomoduler. Denna kåpa ska i så stor utsträckning som möjligt dämpa det fläktinducerade bullret. I det här projektet nyttjas kanaler med ljuddämpare vid ändarna som dämpar ljudet med hjälp av Cremerimpedans, dvs: den väggimpedans som optimalt dämpar en akustisk mod. För att kunna förutspå resultatet skapades en förenklad akustisk modell i ett FEM program. Resultatet från denna modell jämförs sedan med ljudeffektnivån från slutmätningen av den färdiga kåpan. Resultatet från slutmätningen visar att kåpan lyckas sänka radioenheternas totala ljudeffektnivå med 13 dB(A) samtidigt som en temperaturökning på mellan 2.8°C och 5.9°C erhålls. Det här resultatet bedöms vara en framgång, vilket leder till slutsatsen att ljuddämpning med användning av Cremerimpedans rekommenderas för vidare arbete.
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Canagarajah, Cedric Nishanthan. "Digital signal processing techniques for speech enhancement in hearing aids". Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260433.
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Shu, Chin-wei, i 許靜葳. "Suppression of Cleaning Jet Noise". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/11147361962515200107.
Pełny tekst źródłaStreszczenie:
碩士大仁科技大學
環境管理研究所
94
The purpose of this study is to investigate the noise-generating Mechanisms of industrial cleaning jets and to offer possible strategies for the suppression of the generated noise. A set of 6mm-diameter open pipe Nozzles with various lengths and fixtures are used in the experiments. Steel meshes with different densities are used to control the internal turbulences inside the nozzles. It is found that, without adequate control measures, the turbulence existing in the air before it leave the nozzle might be the dominant one among the noise-generating mechanisms, exceeding the widely-studied mixing noise by a large margin. Steel meshes are shown to be an effective tool for the control of the internal turbuence levels.
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"Robust wavelet thresholding for noise suppression". Massachusetts Institute of Technology, Laboratory for Information and Decision Systems, 1996. http://hdl.handle.net/1721.1/3446.
Pełny tekst źródłaStreszczenie:
I.C. Schick, H. Krim.Cover title.
Includes bibliographical references (p. 4).
Supported in part by the Army Research Office DAAL-03-92-G-115 Supported in part by the Air Force Office of Scientific Research. F49620-95-1-0083, BU GC12391NGD
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Rong, Chuang Ruey, i 莊瑞榮. "Speech noise suppression with kalman filter". Thesis, 2000. http://ndltd.ncl.edu.tw/handle/67819278216026490277.
Pełny tekst źródłaStreszczenie:
碩士國立成功大學
電機工程學系
88
With great advance in speech science and the advent of digital cellular telephone, the role of noise suppression in speech processing problems such as speech enhancement and speech recognition has taken on an increased importance. We present a noisy speech model and propose an approach for speech noise suppression. This approach adopts the treating technique for speech with Kalman filter and the spectral subtraction method. It takes the advantage of Kalman filtering method to raise the quality of the treated speech with high-speed variance of noises and eliminates the errors produced by the measuring process and the advantage of spectral subtraction method to reduce the noise level. Experimental results demonstrate the good performance in reducing noise level and lowering distortion of parameter for speech recognition. The performance of our design to treat non-stationary noise is also better than the spectral subtraction method.
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Jung-Fang, Tsai, i 蔡榮芳. "TDMA noise suppression for mobile device". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/vgb3kn.
Pełny tekst źródłaStreszczenie:
碩士國立臺北科技大學
電腦與通訊研究所
99
This thesis introduce how to analysis microphone components, capacitor components, microphone''s input circuit and major noise of cell phone first. The system noises include power noise, cross talk and wireless noise. The TDMA noise of microphone circuit , the normally solve method is to use single end for the input circuit of microphone. To compare the difference of voice quality between differential input and single end input and analysis it with method of theory . In order to solve TDMA noise issue, the thesis will provide the method of complex filter circuit and then do the simulation and measurement of capacitor . By the experiment, it can help us to understand how to choose the best component to solve TDMA noise. To measure the performance of complex high-pass-filter circuit with the high TDMA noise condition and this will help us how to get best performance from high-pass-filter circuit. Finally, we will compare the voice performance with the single end input circuit and differential input circuit for the TDMA noise suppression.
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Lee, Zong-Wei, i 李宗委. "Study of Noise Suppression Materials on the Harmonic Suppression of Filters". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/krz78h.
Pełny tekst źródłaStreszczenie:
碩士義守大學
電子工程學系
102
This study investigates the effect of magnetic Fe3O4 and Ag conductive material mixing with ITK epoxy on the noise suppression of bandpass filters. The bandpass filters is based on half wavelength resonators . The simulator HFSS was employed to simulate the characteristics of filters and the simulated results were compared with experimental results . It is found that the center frequency of filters is not affected after the coating of noise suppression materials ; however , the harmonic of the filters is suppressed with the cated films.
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Tu, Ming-Hsien, i 杜明賢. "Standard Cell Library Noise Characterization and Power Noise Suppression Circuit Design". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/83733414797860377311.
Pełny tekst źródłaStreszczenie:
碩士國立中央大學
電機工程研究所
94
Abstract With advances in semiconductor fabrication technology, the minimum feature size continues to decrease and the circuit density increases gradually. At the same time, increasing clock speeds demands these circuits to switch at faster rates. Thus, noise generation becomes more and more serious in today’s high-speed circuits. Moreover, decreasing power supply voltages dictate lower transistor threshold voltage. Therefore, noise margins of circuits become smaller. It causes a significantly signal-to-noise ratio reduction for both digital and mixed-signal/analog circuits. Therefore, the circuit performance will be limited by noise. In this thesis, we provide a noise-aware standard cell library. There are two major parts in the subject, noise characterization and noise suppression cell design. On noise characterization, we introduce the procedure to characterize the noise behavior and use CLKINVX1 and NAND2X1 as a characterization example. We also discuss the way to characterize simultaneous switching noise and propose some preliminary ideas. On noise suppression cell design, we implement the passive power supply noise (PSN) suppression cell, decoupling capacitance, and an active PSN suppression module. They can be used to suppress PSN occurring in design’s circuit. The simulation results appeal that the active PSN suppression circuit can have 33% reduction for negative PSN peak and 44% reduction for positive PSN peak. Finally, we combine the active PSN suppression circuit with an on-chip bounce measurement circuit. This combined circuit can let us observe the improvement due to the active PSN suppression circuit directly.
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Yang, Pei-Yao, i 楊焙堯. "Study of Noise Suppression in Electromagnetic Flowmeters". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/03257729019961898768.
Pełny tekst źródłaStreszczenie:
碩士國立成功大學
電機工程學系碩博士班
95
Because the electromagnetic flowmeter uses the Faraday’s Law to generate tiny voltage to convert into the flow rate, it has obvious influence on the noise and external interference for measurement’s accuracy. This thesis investigates the method how to suppress the interference. At first the applications and fundamental principle of the electromagnetic flowmeter is given, and followed by the discussion of the factors associated with the operating of system. In the excitatory magnetic driver, first choosing proper exciting method, then suppress the interference which is generated by this excitatory method via choosing the exciting frequency. In the signal circuit, it is processed through filtering, amplifying, and avoiding magnetic interference by sampling technology. Finally, this system obtains a voltage at output of signal circuit. It can be certified that the purpose of the output voltage proportional to the flow is achieved through the experimental results.
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LO, Shun-Teng, i 羅順騰. "Blocking Noise Suppression Schemes for JPEG Images". Thesis, 2002. http://ndltd.ncl.edu.tw/handle/77855472324138344824.
Pełny tekst źródłaStreszczenie:
碩士國立交通大學
電機與控制工程系
90
The image compression by JPEG is very common in our daily life, for example, Internet or the digital camera. JPEG, itself, is a standard of image compression to decrease the data rate. Unfortunately, annoying blocking artifacts would appear. The blocking noise makes us uncomfortable usually. It is necessary and important to remove the blocking noises. The thesis introduces several schemes for the JPEG blocking noise removal: the noise discussed here is the blocking noise resulted from the quantization of DCT coefficients. Traditionally, different filters are applied respectively to the monotone area and the edge area, aiming at smoothing the monotone area or enhancing the edge area. We propose two methods to remove the blocking noise. The first one is the use of the fuzzy rule-based filter (FRB). The fuzzy rule-based filter’s output is a weighted average the processing pixel itself and its neighborhood pixels, dependent on the gray level difference between pixels, the spatial distance and direction between pixels, and the variance in the local window. Using the LMS learning algorithm we can determine the best membership function for the FRB filter. For the second method, we only deal with pixels around the block boundaries, letting the pixels not so blocky. By the simulation results, we have demonstrated the effectiveness and robustness in blocking noise removal our proposal schemes.
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Chen, Yu-Cheng, i 陳昱丞. "Impulse Noise Suppression for DVB-T System". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/83190096339841540147.
Pełny tekst źródłaStreszczenie:
碩士國立中央大學
通訊工程研究所
95
Impulse noise is a kind of noise with short duration and strong interference. It comes from switching on/off electric appliances or the duration of using them. In practical communication system, impulse noise usually causes received signal to distort. If received signal needs the former signal to demodulate the instant signal, impulse noise will influence the later signal. DVB specification defines six different test patterns[2] for impulse noise. This thesis research content is simulation on different DVB-T specification with these test patterns. This thesis first talks about impulse noise detection including convention algorithm, proposed algorithm and then talks about impulse noise cancellation including convention algorithm, S. V. Zhidkov proposed algorithm, this thesis proposed algorithms Least Square (LS) and Search Over Quantization Level (SOQL). By simulating all these algorithm can find that proposed algorithm can effective reduce influence of impulse noise.
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HO, SHENG-TSUNG, i 何昇聰. "Impulse noise suppression for DS-CDMA system". Thesis, 2005. http://ndltd.ncl.edu.tw/handle/08425853292036078772.
Pełny tekst źródłaStreszczenie:
碩士國防大學中正理工學院
電子工程研究所
93
In this thesis, we investigate the techniques for suppressing impulse noise in a direct-sequence code division multiple access (DS/CDMA) communication system. Firstly, we introduce three common impulse noise models—Gaussian Mixture, Middleton Class A and Alpha-Stable distribution, which are proven to best describe the noise characteristic in various physical environment, such as radar, underwater acoustic, radio channels, local networks, wireless and power line communications. Several multiuser detection techniques based on robust regression are explored to combat impulsive noise in DS/CDMA communication systems detection techniques, the adaptive parametric decorrelator is shown to have notable merits for suppressing impulse noise in a varied communication. By choosing proper basis functions, the parametric detector can adjust itself to effectively suppress the impulse noise. Simulations show that the performance approaches to the optimum in the three kinds of impulsive noise environments.
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Liou, Tau-Chian, i 劉陶謙. "Duct Noise Suppression Using Passive Silencing Techniques". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/yzfknd.
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碩士國立臺灣海洋大學
機械與機電工程學系
103
This study aims to investigate the noise emitted by the machine’s inlet and outlet ports, with the quarter-wave resonator and the Herschel-Quincke tube applied for noise suppression. Finite element simulation is conducted for the cavity and the duct for sound transmission loss analysis. The ways to achieve broadband silencing effect are examined for a specified noise frequency. By increasing the cross-sectional area due to the increase in the number of silencers used, performance of both the quarter-wave resonator and the Herschel-Quincke tube is improved. The quarter-wave resonator is superior to the Helmholtz resonator in that the former only requires the tube length to be specified, whereas the latter requires the design of the cavity volume which is affected by the neck area chosen. The quarter-wave resonator is applied in the experiment for noise suppression of a portable vacuum cleaner. The silencer is created using the 3D printing technology. Because it is difficult to print a large model using 3D printing, the shape of the resonator is revised accordingly, which results in slight deviation of the originally designed main frequency. However, the performance is not severely affected due to the broadband design. Experimental study includes the traditional sound pressure measurement, three- microphones, and four-microphone measurements. Based on the observation of both the experiment and computer simulation, it is demonstrated that Herschel-Quincke tube is more effective than the quarter-wave resonator in terms of effective band width and actual implementation. Noise suppression of a hand dryer is thus conducted using the Herschel-Quincke tube.
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Chen, Chih-Neng, i 陳智能. "Filter design for suppression of noise propagation". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/22880719001430544958.
Pełny tekst źródłaStreszczenie:
碩士國立臺灣大學
電機工程學研究所
92
This thesis outlines the design and development of filters applies to medical electronic devices, which leads to a better design and rapid development architecture for the inhibition of electromagnetic interference (EMI). The EMI referred included the device induced and those that existed in our environment. The filters have been constructed with the objective of preventing incorrect data acquisitions and measurements due to the EMI and will increase the reliability and precision of such devices. A comprehensive introduction of the EMI induced noise and their transmission route is revealed along with a thorough analysis and configuration of an existing consumer product. The new method proposed has greatly reduced the time required for research and design resulting from the fact that adjustments to eliminate noise would no longer be necessary after the design is completed. Recurrent corrections avoided would then accelerate the promotion of the newly designed device into the consumer market. The implemented filter undergoes laboratory tests, simulations and functional corrections in order to meet all EMI regulations. The final product not only meets the anticipated results, but also gives designers in the field of medical electronic devices a better solution for EMI reductions.
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Wu, Tzong-Yow, i 吳宗佑. "Study of DSP-Based Suppression Conducted Noise". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/27135902686915624638.
Pełny tekst źródłaStreszczenie:
碩士國立成功大學
電機工程學系
87
In the thesis, a device is developed to decipher commode-mode noise and differential-mode noise from a conducted EMI noise measurement, its basic principles of the separator will be described. Based on the analysis of the conducted EMI source and equivalent circuit, an simplify design process and suitable EMI filter is described for a single-phase active power filter. Otherwise, an active noise filter is also designed based on digital signal processor. Since it is difficult to know the exact noise component, so adaptive filter theory is the most suitable one to realize the active noise cancellation. At the end of the thesis, the FIR LMS and Filtered-X LMS structure algorithm will be mentioned and use a digital signal processor to implement noise cancellation to show the realizability of the theory.
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Wu, Yenwun, i 吳衍文. "Effect Of Fe3O4 On High Frequency Noise Suppression". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/91493420737740266794.
Pełny tekst źródłaStreszczenie:
碩士義守大學
電子工程學系
100
This study investigates the effect of Fe3O4 on high frequency noise suppression. The simulator HFSS is employed to investigate the structure and the parameter of magnetic materials and the results were compared with experimental ones. The thickness and conductivity of magnetic films are two important factors in determining the noise suppression. For FR-4 substrate coated with magnetic material Fe3O4, the noise suppression can reach 54% at 10GHz. The result shows that noise suppression can reach 95% at 10GHz for the specimens doping 50wt% conductive silver.
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Chen, Yi-Kang, i 陳億剛. "Study on Radio-Frequency Integrated Circuits Noise Suppression". Thesis, 2001. http://ndltd.ncl.edu.tw/handle/70122925255337340698.
Pełny tekst źródłaStreszczenie:
碩士國防大學中正理工學院
電子工程研究所
89
The purpose of this work is to study substrate noise interfering effect for silicon-based RFICs operation at high frequency. In addition to reduce the influence of substrate noise between digital and analog circuits in RFICs, several substrate noise suppression techniques are considered. In the study, scattering parameters S21 are measured by network analyzer HP8510C to analyze substrate noise forward transmission characteristics. In addition, a commercial device simulation tool ATLAS is used to compare measured results and to predict high-frequency noise-coupling characteristics of various test structures for future applications. Experimental results indicate that grounded P+ guard rings play a role to evacuate noise from substrate to ground, and exhibit very good characteristics in suppressing substrate noise with simple process procedure. The isolation effect of grounded N-well is not as phenomenal as P+ guard rings. Among all test structures, N+ pocket structures with high doping concentration exhibit the strongest noise reduction capability.
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Jhou, Shih-Gang, i 周世剛. "Intake Noise Suppression of a High Speed Fan". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/99eny8.
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Wang, Jing-Yi, i 王靖宜. "Intake and Exhaust Noise Suppression Using Destructive Interference". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/h23aj3.
Pełny tekst źródłaStreszczenie:
碩士國立臺灣海洋大學
機械與機電工程學系
103
This study deals first with the annoying noise generated by the motor driven blades of a portable vacuum cleaner by using the noise interference principle of the Herschel-Quincke tube. Both the theoretical and experimental approaches were utilized for effective noise suppression. In consideration of the size limitation of the vacuum cleaner, the dimensions of the interference silencing device were restrained not to protrude outside the main body. We designed double sets of Herschel-Quincke tube targeting the main noise frequency 725 Hz. Finite element simulation was conducted to examine the 3D sound field characteristics. The sound transmission loss between the inlet and outlet can thus be assessed. The actual designed model was created using a 3D printer. The experiment confirmed the excellent silencing performance. Originally the measured noise of the vacuum cleaner is 81.6 dBA, which is suppressed down to 73.8 dBA, a 7.8 dBA reduction, after applying the interference silencing strategy proposed in this study. The overall noise can be further reduced down to 73 dBA, i.e. an 8.6 dBA reduction, by fine-tuning the exhaust port based on Fluent flow field analysis and experimental observation, while still maintaining the original system performance. Sound intensity measurement technique was utilized to identify the main source noise of the vacuum cleaner for further improvement. The total noise is further suppressed down to 72.5 dBA, a 9.1 dBA reduction. This demonstrates further improvement of the silencing performance. The flow velocity and the pressure measured at the intake showed no significant changes, hence the performance of the original system has not been compromised due to the installation of the noise control device. The interference silencing technique was applied to improve the intake noise of a hand dryer. Originally the measured noise of the hand dryer is 76.1 dBA. After the Herschel-Quincke tube is installed and an appropriate intake port orientation is selected, the total noise is suppressed down to 72.2 dBA, i.e. a 3.9 dBA reduction. Future work can be conducted to further improve the noise suppression performance by increasing the cross sectional area and by smoothing the flow field in the duct.
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Hsu, Sheng-Wei, i 許勝為. "Study of Graphene on High Frequency Noise Suppression". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/j5u84x.
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Wu, Jung-Piao, i 吳榮標. "Noise Suppression Techniques for PFC/PWM Combo IC". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/55865008013481924101.
Pełny tekst źródłaStreszczenie:
碩士國立臺灣科技大學
電子工程系
104
This thesis is proposed to investigate the noise suppression techniques for a PFC/PWM combo IC. When powers on, input current transient noise interferes a 400-W power supply unit’s current sampling and causes the power MOSFET malfunction or damage. Thus, the PFC circuit is modified to suppress the noise according to the measured abnormal signals. After modified, the new design circuit validated at different temperature environments, power sources, and voltage conditions is implemented. As a result of validation, the noise in input current is improved, and the most important of all, the MOSFET of power factor corrector boost circuit would not switch disorder even if the noise exists. The PFC/PWM combo IC can work normally.
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Dong-Ming, Ou, i 歐東明. "Image Compression with a Consideration of Noise Suppression". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/73277616657799004575.
Pełny tekst źródłaStreszczenie:
碩士國立中山大學
電機工程學系
87
In this research , the Kalman Filter is exploited for restoring image against noise corruption . The parameters of the signal model in the Kalman Filter is obtained by our developed segmentation technique which segment the origianl image for computing the image structure of individual region. The image structure are defined to be the linear relationship between pixels with their upper and left neighbors. Image can be very inhomogeneous. However, the image structure may be uniform enough in some image components. By this image texture, individual image constraint equations can be set up for those triple pixel. These equations are the property vectors choosen by us for segmentation decision. Discrepancy between equations are measured by sequential least square method. A recursive method for computing the error is develop in this thesis for simplifying computation. In the field of image processing , Kalman Filter is used for optimal estimation of image corrupted by additive noise. We segment the image by it's local property. By our segmentation technique every region has it's specific image structure, which will be system parameters of Kalman Filter. In this sense , every region has it's suitable Kalman Filter. Therefore the restored image is better in value and in visual effects by our method. Mean time, the number of segmente region for Kalman Filter of the original image is reasonable around 40, thus the original image is compressed to the image structure of the segmented region.