The study investigated the feasibility of including DPOAEs in the annual medical surveillance test battery for the identification of NIHL in a group of employees in a manufacturing industry in KwaZulu-Natal. Feasibility was investigated by exploring the sensitivity, specificity and predictive efficiency of DPOAEs, the ability of DPOAEs to detect subtle noise-induced cochlea changes, the test-retest reliability of DPOAEs and lastly, the duration of time taken to conduct the DPOAE test bilaterally. A cross-sectional and repeated measures within-in participant design was utilized in the study. A purposive convenience sampling technique was used, as well as a stratified sampling approach in order to realize objective two of the study. The study consisted of 60 participants, which were further stratified into four test groups, i.e. Group A: 0-3 years, Group B: 3.1-6 years and Group C: 6.1-9 years and Group D: 9.1-13 years of working within the beverage manufacturing industry. A high sensitivity and negative predictive value was reported in the current study, suggesting that DPOAEs may be able to identify those who present with subtle cochlea changes as a result of exposure to occupational noise. The sensitivity of DPOAEs was 100% at 1, 2, 4, 6 and 8kHz in the right ear and at 4 and 6kHz in the left ear. The specificity of DPOAEs in the current study ranged between 55%-97% across the frequency range in the right ear and 49%-88% in the left ear. A negative predictive value of 100% was obtained bilaterally across the frequency range, except at 8kHz in the left ear. Visual inspection of the DPgram in the current study revealed a bilateral reduction in DPOAE amplitudes for all test groups in the high frequency region of the DP-Gram, namely, 5477Hz and 7303Hz, in the absence of a statistically significant difference (p>0.05). A greater frequency range appears to be affected in this group of workers, indicating that the type of noise, namely, impulse noise, may result in cochlea changes. Corresponding changes on the pure tone audiogram were not observed, however, noise notch configurations were observed for the groups with a longer history of noise exposure. This was not seen bilaterally as is typically expected with NIHL. Good test-retest reliability across the frequency range obtained in the current study further indicates the feasibility of including DPOAEs in the annual medical surveillance test battery. Additionally, the current study calculated an average of 86 seconds (1 minute 26 seconds) to conduct the DPOAE test bilaterally, confirming that DPOAEs are a quick test to administer. The findings of this study suggest that DPOAEs may be used to monitor early subtle noise-induced cochlea changes for workers exposed to noise in the beverage manufacturing industry as part of the annual medical surveillance test battery. / Thesis (M.Comm.Path.)-University of KwaZulu-Natal, Westville, 2013.

We address the problem of image denoising for additive white Gaussian noise (AWGN), Poisson noise, and Chi-squared noise scenarios. Thermal noise in electronic circuitry in camera hardware can be modeled as AWGN. Poisson noise is used to model the randomness associated with photon counting during image acquisition. Chi-squared noise statistics are appropriate in imaging modalities such as Magnetic Resonance Imaging (MRI). AWGN is additive, while Poisson noise is neither additive nor multiplicative. Although Chi-squared noise is derived from AWGN statistics, it is non-additive. Mean-square error (MSE) is the most widely used metric to quantify denoising performance. In parametric denoising approaches, the optimal parameters of the denoising function are chosen by employing a minimum mean-square-error (MMSE) criterion. However, the dependence of MSE on the noise-free signal makes MSE computation infeasible in practical scenarios. We circumvent the problem by adopting an MSE estimation approach. The ground-truth-independent estimates of MSE are Stein’s unbiased risk estimate (SURE), Poisson unbiased risk estimate (PURE) and Chi-square unbiased risk estimate (CURE) for AWGN, Poison and Chi-square noise models, respectively. The denoising function is optimized to achieve maximum noise suppression by minimizing the MSE estimates. We have chosen the bilateral filter as the denoising function. Bilateral filter is a nonlinear edge-preserving smoother. The performance of the bilateral filter is governed by the choice of its parameters, which can be optimized to minimize the MSE or its estimate. However, in practical scenarios, MSE cannot be computed due to inaccessibility of the noise-free image. We derive SURE, PURE, and CURE in the context of bilateral filtering and compute the parameters of the bilateral filter that yield the minimum cost (SURE/PURE/CURE). On processing the noisy input with bilateral filter whose optimal parameters are chosen by minimizing MSE estimates (SURE/PURE/CURE), we obtain the estimate closest to the ground truth. We denote the bilateral filter with optimal parameters as SURE-optimal bilateral filter (SOBF), PURE-optimal bilateral filter (POBF) and CURE-optimal bilateral filter (COBF) for AWGN, Poisson and Chi-Squared noise scenarios, respectively. In addition to the globally optimal bilateral filters (SOBF and POBF), we propose spatially adaptive bilateral filter variants, namely, SURE-optimal patch-based bilateral filter (SPBF) and PURE-optimal patch-based bilateral filter (PPBF). SPBF and PPBF yield significant improvements in performance and preserve edges better when compared with their globally-optimal counterparts, SOBF and POBF, respectively. We also propose the SURE-optimal multiresolution bilateral filter (SMBF) where we couple SOBF with wavelet thresholding. For Poisson noise suppression, we propose PURE-optimal multiresolution bilateral filter (PMBF), which is the Poisson counterpart of SMBF. We com-pare the performance of SMBF and PMBF with the state-of-the-art denoising algorithms for AWGN and Poisson noise, respectively. The proposed multiresolution-based bilateral filtering techniques yield denoising performance that is competent with that of the state-of-the-art techniques.

This thesis deals with the study and normative proposal for a regulation of noise pollution generated by merchant ships, which is the main cause of underwater noise pollution. It is divided into three chapters. In the first chapter, the aspects of marine acoustics are reviewed, including a revisit of hydrophones, the analysis of the distances at which sound intensities are maintained above a baseline level, and a self designed study, which leads to the conclusion that the differences in incremental trends in underwater sound intensity in previous studies are due to differences in maritime traffic. This is confirmed by highly significant statistical data obtained by binary logistic regression between hydrophonic records that have detected an increase and those that have not (p<0.0001). A compilation and bibliometric analysis has made it possible to study specifically the negative impact of ship-generated noise on marine species. In 87% of the publications consulted, including experimental data, a high or moderately high negative impact of sound on marine species was evident; only 5% of the articles reported no effects of noise pollution. The study covered a wide variety of seas and oceans, although most of the studies (31%) were conducted using cages or similar. The research was mainly conducted on fish (43%) and mammals (38%). Behavioural changes were recorded in 59% of cases, physical changes in 11%, masking in 11% and combined changes in 14%. Four levels of underwater sound intensity are proposed: Environmental zone 0 (no appreciable anthropogenic pollution), from baseline level (30 dB) to 80 dB. Zone A of acceptable (low) pollution, from 81 dB to 175 dB (threshold of potential damage). Zone B of tolerable, but potentially harmful sound intensities (between 176 dB and 195 dB) and a Zone C of risk of permanent injury (above 195 dB, permanent injury threshold); vessels generating intensities at this level should be penalised or even banned. A way forward for the future regulation of underwater noise pollution is suggested, through a concerted effort via a global track derived from the UN in collaboration with specialised global and EU organisations, including the Baltic Sea registers, and legal support from the experts of the World Commission on Environmental Law. Its implementation should be carried out through the International Maritime Organization IMO).

The master’s thesis deals with the noise diagnostic in the solar cells. Describes the main kinds of noises. The samples were quality and reliability screened using noise reliability indicators. The samples were surveyed by measuring the I-V characteristics, the noise spectral density as a function of forward voltage and frequency. It was calculated the noise spectral density as a function of forward current.

Orientador: Stelamaris Rolla Bertoli / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-05T23:46:28Z (GMT). No. of bitstreams: 1 Santos_Christiandos_M.pdf: 3511506 bytes, checksum: d365f6dc71d5566b93533834923018e0 (MD5) Previous issue date: 2004 / Resumo: A existência de fenômenos acústicos depende de três fatores: a fonte, o meio e o receptor. Para a prevenção de condições ruidosas em certos ambientes, é necessário o conhecimento de uma característica própria da fonte que não sofre interferência do meio na propagação da energia sonora, como é o caso da potência sonora. O IBAMA em conjunto com o INMETRO iniciou um programa que visa informar e minimizar o ruído (nível de potência sonora) produzido por aparelhos elétricos etiquetando-os. Este programa se chama Selo Ruído. Existe uma previsão de inclusão de ferramentas elétricas neste programa de etiquetagem. A furadeira elétrica é uma destas ferramentas que tem inclusão prevista. Com o intuito de investigar os métodos de ensaio para determinação de potência sonora, este trabalho propõe a realização de ensaios de diversos métodos normalizados de determinação de nível de potencia sonora aplicando-os para furadeiras elétricas. Os métodos escolhidos para os ensaios foram os que utilizam salas reverberantes especiais (ISO 3743 ¿ Engineering Methods for Special Reverberations test Rooms e ISO 3741 ¿ Precision Methods for Special Reverberations test Rooms). Estes métodos são referenciados na norma nacional NBR 13910:1997-Parte 1- Diretrizes de ensaios para a determinação de ruído acústico de aparelhos eletrodomésticos e similares. Com os resultados obtidos dos ensaios realizados, foi feita uma análise de qualificação das metodologias empregadas. A partir de cada item destas metodologias foi analisada a aplicabilidade destes itens a ser empregado no método de ensaio proposto. A construção das etapas do método foi obtida a partir dos itens qualificados e aplicáveis ao programa de etiquetagem Selo Ruído / Abstract: In the acoustic phenomena there are three main variables: the source, the medium and the receptor. For the prevention of noise conditions in certain places, it is necessary to know a source characteristic that does not change with medium variations. This characteristic is the sound power radiated by the source. To consider this prevention, IBAMA and INMETRO started a program that labels the household appliances according to the noise level emitted by them. This program is called ¿Selo Ruído¿. There is a prevision to include the electric tools in this label program. The drill is one of these electric tools that will be included. To investigate the methods for determination of the sound power levels, this work proposes some tests of drills in several standarded methods. The methods used for the tests were the ones that use reverberation rooms (ISO 3743 ¿ Engineering Methods for Special Reverberations test Rooms and ISO 3741 ¿ Precision Methods for Special Reverberations test Rooms). These methods are referenced at the Brazilian standard NBR 13910:1997 ¿ Part 1 ¿ ¿Diretrizes de ensaios para a determinação de ruído acústico de aparelhos eletrodomésticos e similares¿. A qualification analysis of the methodologies applied was done, based on the tests results. An application of these items was done from each item of these methodologies in the test method proposed. The construction of the steps in the proposed method was made from the items qualified and applied to the ¿Selo Ruído¿ program / Mestrado / Edificações / Mestre em Engenharia Civil

published_or_final_version / abstract / Transport Policy and Planning / Master / Master of Arts in Transport Policy and Planning

Exterior vehicle noise has a very big impact when it comes to environmental noise pollution. Due to the decrease of the other noise sources of a passenger car, like power-train and air turbulence noise in the last decade, the tyre/road noise has become a more important part in the overall noise generation of a vehicle nowadays. It is considered as the main noise source in nearly all driving conditions, especially with increasing vehicle speed. The easiest idea to tackle this pollution is to introduce rules like speed-limits to control the noise at a certain area or time. More interesting, however, is to approach the problem of unwanted noise directly at the source. This Thesis, carried out at Loughborough University, aims to give a better understanding about the basic noise generation mechanisms at the tyre/road interface. Especially, the air related mechanisms of closed cavities are analysed. With the usage of a solid rubber tyre, unique measurements have been carried out and the results are compared to the theories already existing in the literature. These measurements reveal some of the strengths and weaknesses of the current understanding of air related noise generation.

Speech processing in the automotive environment is a challenging problem due to the presence of powerful and unpredictable nonstationary noise. This thesis addresses two detection problems involving both nonstationary noise signals and nonstationary desired signals. Two detectors are developed: one to detect passing vehicle noise in the presence of speech and one to detect speech in the presence of passing vehicle noise. The latter is then measured against a state-of-the-art voice activity detector used in telephony. The process of compiling a library of recordings in the automobile to facilitate this research is also detailed.

Thesis (M.Sc (Physiology)) --University of Limpopo, 2015 / Objective This study assesses whether noise levels above legal limits of 85 dB(A) that can result in noise-induced hearing loss are present in areas where employees are supposed to work and to verify that such areas are demarcated as noise zones at the Polokwane Platinum Smelter. Background and motivation Excessive noise is a global health hazard with considerable social and physiological impact, including the development of noise-induced hearing loss (NIHL). Noise is a major hazard in many workplaces. It is estimated that more than 30 million workers (almost 1 in 10) are exposed to unsafe noise in their work places. NIHL is the second most self-reported occupational illness or injury in the United States. Amongst miners, more than 90% of the population reports hearing problems by the age of 55 years. Noise exposure is prevalent in construction, foundries, agriculture, transport, industry and mining-related activities. The prevalence of NIHL has not changed much in the past two decades. Therefore, a hearing conservation programme is an important issue in the smelter as certain areas are denoted as noise areas. Study design A cross-sectional study design with a group of utility workers at the Polokwane Platinum Smelter, as the experimental group, and a group of undergraduate Bachelor of Science students at the University of Limpopo (Turfloop Campus) served as a control group. Method A sound level meter was used to measure the noise levels where the utility group performs their technical work. Data were analysed using the Statistical Package for the Social Sciences (SPSS) computer program. Results The average noise measured in various locations of the Polokwane Platinum Smelter was between 62.6 dB(A) and 105.1 dB(A). The results indicated that workers at the Polokwane Platinum Smelter are over exposed to noise in certain work areas if they work eight hours in the area. Areas where the average noise level was above noise rating limit of 85 dB(A) were demarcated as noise zones as an additional protective measure. Employees also use hearing protective devices, when they are working in noise zones, to control personal noise exposure. This is in accordance with the Occupational Health and Safety Act No. 85 of 1993 as amended eleventh edition (OHS Act 85/93). Conclusion In the present study, noise levels in certain areas exceeded the noise rating limit of 85 dB(A). However such areas are clearly demarcated as noise areas and employees accessing those area must wear earmuffs or earplugs. Possibilities of employees developing hearing loss overtime exist, if employees work for eight hours or longer in demarcated areas and do not adhere to the existing Hearing Conservation Program (HCP) implemented at the Polokwane Platinum Smelter. Noise levels at the Polokwane Platinum Smelter should be monitored regularly. / University of Limpopo

The development of major commercial airports promotes the air transport industry and generates positive economic benefits to the airport and to its host economy. However, external costs are associated with these benefits. Any increase in aircraft movement causes negative environmental impacts, especially noise pollution. Governments have reduced aircraft noise levels at their sources, or introduced aircraft noise management strategies (ANMS); however the problems have never been satisfactorily resolved. This research aims at developing a better understanding of the impacts of aircraft noise on community health and well-being by exploring two core research questions: (1) ???Is health related quality of life worse in communities chronically exposed to aircraft noise than in communities not exposed????; and (2) ???Does long-term aircraft noise exposure associate with adult high blood pressure level via noise stress as a mediating factor????. The Sydney (Kingsford Smith) Airport has been selected as a case study. The health survey instruments have been developed and piloted, and then translated from English into Greek and Arabic. A postal self-administrative health survey (with follow-up letters) has been implemented in the areas surrounding Sydney Airport (called ???aircraft noise exposure group???) and in the matched control group. The total sample size was 1,500 with 47% response rate. This thesis has developed a ???new??? noise index (named Noise Gap Index, NGI) to describe and assess aircraft noise in such a way that is easily understood by the layperson. Factorial analysis of covariance revealed that ???Health related quality of life, in term of physical functioning, general health, vitality, and mental health, of community chronically exposed to high aircraft noise level were worse than the matched control area???. Binary logistic regression analysis found that ???Subjects (aged 15 ??? 87) who have been chronically exposed to high aircraft noise level have the odds of 2.61 of having chronic noise stress. In addition person who have chronic noise stress have the odds of 2.74 of having hypertension compared with those without chronic noise stress???. Finally, the robust hypotheses of effects of aircraft noise on community health and well-being for future experimental study were proposed.