Noise-induced hearing loss (NIHL) is one of the most common illnesses that is frequently reported in the occupational and military sectors. Hearing loss due to high noise exposure is a major health problem with economic consequences. Industrial and military noise exposures often contain high-level impulsive noise components. The presence of these impulsive noise components complicates the assessment of noise levels for hearing conservation purposes. The current noise guidelines use equal energy hypothesis (EEH) based metrics to evaluate the risk of hearing loss. A number of studies show that the current noise metrics often underestimates the risk of hearing loss in high-level complex noise environments. The overarching goal of this dissertation is to develop advance signal processing based methods for more accurate assessments of the risk of NIHL. For these assessments, various auditory filters that take into account the physiological characteristics of the ear are used. These filters will help to understand the complexity of the ear’s response to high-level complex noises.

[pt] Nesta dissertação foram projetados e desenvolvidos osciladores apresentando ruído de fase otimizado. Em virtude das limitações dos equipamentos analisadores de espectro na precisa medição do ruído de fase dos osciladores desenvolvidos nos laboratórios do CETUC, foi implementada a técnica de medição Método do Detector de Fase. Esta técnica consiste no desenvolvimento de um segundo oscilador com as mesmas características do existente, e com auxílio de misturadores, realizar o batimento dos mesmos para freqüências próximas a DC, onde nesta região a medição do ruído de fase torna-se viável. Entretanto, em aplicações dedicadas, verificou-se que o batimento entre dois osciladores operando em torno de 10 GHz produz uma freqüência intermediária instável, variando de 10 kHz à 50 kHz. Para evitar a realização de uma medição extremamente instável, utilizou-se o método de sincronização de freqüências (Injection Locking) entre os osciladores. Foi também destacada a influência do ruído de cintilação (Flicker Noise) na medida final do ruído de fase. A melhor medida aferida foi em torno de -100 dBc/Hz @ 3,25 kHz. Foi verificado através de diversas simulações que a freqüência de cintilação int c f , situada em 10 MHz, apresenta grande influência sobre as medições do ruído de fase realizadas à 3,25 kHz da portadora, degradando-o em cerca de 30dB. / [en] In this dissertation, oscillators presenting optimized phase noise had been projected and develloped. Because of the limitation of the specter analyzer devices in the accurate measurements of the oscillators phase noise developed in the CETUC laboratories, it was implemented the measurement technique called Phase Detector Method. This technique consists on the development of a second oscillator with the same characteristics of the already existent one and, with aid of mixers, multiplies these signals together and provides the difference of the two signals next to DC, where, in this region, the measurement of the phase noise becomes viable. However, in dedicated applications, it was verified that the beating between two oscillators operating around 10GHz produces instable intermediate frequency, varying between 10kHz to 50kHz. To prevent the accomplishment of an extremely unstable measurement, the method of synchronization of frequency (Injection Locking) between the oscillators was used. Also the influence of the Flicker Noise in the final measure of the phase noise was detached. The best measure was around -100dBc/Hz@3,25kHz. It was verified through lots of simulations that the flicker corner frequency int c f , situated in 10MHz, presents great influence on the measures of the phase noise carried through to the 3,25kHz of the carrier, degrading it in about 30dB.

[pt] A pesquisa analisou o ruído urbano e suas implicações, e o Estudo de Impacto de Vizinhança, suas necessidades e mecanismos necessários a sua realização, assim como os problemas que podem advir da implantação de novos empreendimentos pela falta de regulamentação das prefeituras que não o adotaram dentro das suas políticas e estratégias relacionadas à urbanização das cidades, onde em razão da crescente industrialização e ampliação dos estabelecimentos comerciais, sem qualquer planejamento prévio. Dentro dos parâmetros impactantes, com a implantação do Estudo de Impacto de Vizinhança analisamos o ruído urbano e as implicações geradoras do incomodo sonoro, uma vez que o aumento dos níveis de ruído é crescente e fruto do crescimento desordenado das cidades. / [en] Noise pollution according to WORLD HEALTH ORGANIZATION (1980) after air and water pollution, is the environmental problem that affects the greatest number of people. It is noticeable the increase in discomfort due to noise and the damage this has caused people in their city environment. With industrial and technological development, various sources of environmental pollution have been causing damage to humans and the environment. From the 70s onwards, noise started to be perceived with greater attention in urban centers as an important agent that attacked the environment and people s health, especially in the most populated cities. The relevance of the noise pollution theme is increasingly significant, as it generates damage that can be irreversible. It is worth mentioning that it is almost impossible to be in big cities and not be disturbed by expressively loud sound sources. In 1980, the World Health Organization treated noise pollution as a cause among the main problems on the planet. He also mentioned that the appearance of insomnia, in addition to a series of harmful health effects such as stress, depression, hearing loss, loss of concentration, memory loss, headaches, increased blood pressure, tiredness, gastritis and ulcers, fall in school and work performance. The fact that must be taken into account is that noise pollution is not a simple problem related to our comfort, but to physical and mental health, where the general population is not at all aware of the existing risks, facing with resignation being a consequence of living in a modern world with risks, among them is the exposure of citizens to the effects of noise pollution.

The Filtered-X Least-Mean-Square (FXLMS) algorithm is widely used in active noise control due to its robustness, simplicity, and ability to be implemented in real time. In a feedforward implementation of the FXLMS algorithm, a reference signal that is highly correlated with the noise to be controlled is filtered with an estimate of the transfer function of the secondary path. The convergence characteristics of the FXLMS algorithm have been well studied. A convergence parameter is used to optimize the convergence of the algorithm. However, the optimal value for the convergence parameter is frequency dependent. Thus for noise containing multiple tones at different frequencies the convergence parameter can only be optimized for one of those tones. Other tones will have slower convergence rates and in general less attenuation than they would have if they were treated singly and parameters could be optimized for those frequencies separately. A method is developed to modify the magnitude response of the secondary path estimate while maintaining the original phase response, which equalizes the convergence characteristics over multiple frequencies, giving more uniform convergence and attenuation for all tones being controlled. Stability of the algorithm is not compromised. The modification to the FXLMS algorithm is relatively simple to implement and has been shown to increase overall attenuation of a signal containing multiple tones by an additional 6-9 dB.

Active noise control (ANC) has been implemented using analog filters to reduce broadband noise from a small axial cooling fan. Previous work successfully attenuated narrow-band, tonal portions of the noise using a digital controller. The practical performance limits of this system were reached and it was desirable to attenuate the noise further. Additional research, therefore, sought to attenuate broadband noise from the fan using a digital controller, but performance was limited by the group delay inherent in the digital signal processor (DSP). Current research attempts to further attenuate broadband noise and improve performance of the system by combining the tonal controller with an analog feedback controller. An analog controller is implemented in parallel with the digital controller without degrading the performance of either individual controller. Broadband noise is attenuated in a certain frequency region, but at the expense of increasing noise in adjacent frequency regions. Results show that a single-input single-output (SISO) controller is preferable to a multiple-input multiple-output (MIMO) controller for this system.

Oljud i hemmet är något som kan ge psykiska men även fysiska problem vid lång exponering. I byggbranschen finns det många moment som ger ifrån sig höga ljudnivåer som ofta pågår under en längre tid. Detta kan leda till att många upplever byggarbetsplatser i anslutning till hemmet som ett stort störningsmoment. Byggbranschen är en väldigt prispressad bransch där att vara kostnadseffektiv oftast kommer först. Kunderna kräver en billig produkt och detta kan leda till att saker som bullerreducering för boende i området prioriteras bort. Idén till detta arbete kom från att en av författarna till detta arbete var bosatt i ett område där oljud från en närliggande byggarbetsplats var ett stort problem. Detta blev uppmärksammat och ledde till att de boende i området fick minskad hyra som kompensation under byggnationen.  Syftet med arbetet är att undersöka hur det buller som uppstår i produktion påverkar de boende och vad som görs för att minska detta. Metoden som har använts är omvärldsanalys samt intervjuer med folk ifrån branschen.  Vår undersökning visar att buller inte är något som de företag som intervjuades har i åtanke under planeringsfasen. Det enda som de gör aktivt är att hålla sig till normala arbetstider och att dela ut information till närliggande fastigheter när ett större arbete ska utföras som kommer att påverka de boende runtomkring. Den utveckling som sker i branschen är oftast en biprodukt av en utveckling i andra fält, det sker inget speciellt arbete för att minska buller för boende. Nya maskiner och fordon togs upp som exempel på några förbättringar. Prefab kan vara ett intressant sätt att minska bullernivåerna på eftersom det lever upp till branschens krav om minskad kostnad samtidigt som bullret minskas.   Slutsatsen är att man ej aktivt jobbar med att reducera buller för de boende. Inget arbete sker från byggföretagen med att motverka buller för de boende utan det som sker är en biprodukt av utvecklingar i verktyg och fordon. Buller har en negativ påverkan på de boende och kan leda till psykiska men även fysiska besvär. / Noise in the home is something that can cause mental but also physical problems with long exposure. In the construction industry there are many elements that emit high noise levels that often last for a long time. This can lead to many people experiencing construction sites in connection with the home as a major disruption. The construction industry is a very price squeezed industry where being cost effective usually comes first. Customers demand a cheap product, this can lead to things like noise reduction for residents in the area being prioritized away. The idea for this work came from the fact that one of the authors of this work lived in an area where noise from a nearby construction site was a major problem. This was noticed and led to the residents in the area receiving reduced rent as compensation during construction.  The purpose of the report is to investigate how the noise that arises in production affects the residents and what is done to reduce this. The method that has been used is external analysis and interviews with people from the industry. The result of this thesis was that noise is not something that the companies interviewed have in mind during the planning phase. They follow the working hours required by law and in some cases, information is distributed about future work. The development that takes place in the industry is usually a by-product of development in other fields, but there is no special research made to reduce noise levels for people living nearby. New machines and vehicles were mentioned as examples of some improvements. Prefab can be an interesting way to reduce noise levels because it lives up to the industry's demand for reduced costs while reducing noise.  The conclusion is that they do not actively work to reduce noise for the residents. No work is done by the construction companies to counteract noise for the residents, but what is being done is a by-product of developments in tools and vehicles. Noise has a negative impact on the residents and can lead to mental but also physical problems.

Syftet med litteraturstudien var att undersöka hur buller påverkar sjukhusmiljön med hänseende på vårdpersonal och patienter. Studiens avsikt omfattar även en undersökning av vårdpersonalens och patienters eventuella olika uppfattningar angående buller. Effekterna av buller och dess omfattning inom vårdavdelningsmiljön har också undersökts. Resultatet av studien visar på att bullermiljön på sjukhus överskrider de riktlinjer för buller som WHO fastslagit. Vidare visar studien på indikationer på att brittiska sjuksköterskors kunskap angående fenomenet buller är bristfällig. Sjuksköterskors och patienters uppfattningar av buller varierar till viss del. / The aim of this study was to examine how noise effects the hospital environment with regards to nursing staff and patients. The aim also includes nursing staff’s and patients’ possible different perceptions’ of noise. The extent and effect of noise on the ward have also been studied. The result of the study shows that the noise environment of the hospital. exceeds the recommended guidelines set by the WHO. Furthermore the study indicates that nurses in the UK have poor knowledge about the noise phenomenon. Nurses ‘and patients’ perceptions’ regarding noise differ to some degree.

Predictors of people’s responses to noise inside cars are used by car companies to identify and address potential noise problems from tests. Because significant advances have been made in the reduction of engine, powertrain, and tire/road noise, it is now important to pursue reductions in wind or aerodynamic noise. While models of loudness are commonly used to predict people’s responses to stationary wind noise, some wind noises are less acceptable than is predicted by the loudness metric. Additional sound characteristics may account for this. The research described in this dissertation was conducted in two main stages. The focus of the first stage was on improving acceptability predictions for stationary noise, by using additional sound quality metrics along with predictions of loudness. Three listening studies were designed and conducted, including one study with aspiration noise. Test sounds were a combination of recordings made on cars in a wind tunnel and modified recordings. Methods to modify individual sound characteristics were developed to de-correlate metrics across the set of test sounds, and to examine trends of acceptability with particular sound characteristics. Models of acceptability for stationary wind noise are significantly improved when a metric that predicts the sharpness of a sound is included in the model with the loudness metric. The focus of the second stage of the research was on improving acceptability predictions for non-stationary noise, particularly noise with the kind of variations that are expected from wind gusts. A simulation method was developed to generate sounds with controlled gusting features by modifying stationary noise recordings. Two listening studies were conducted containing simulated gusting sounds, and a gusting unacceptability metric was designed to predict subjects’ responses based on the strength, modulation rate, and duration of the gusts. The inclusion of this gusting metric significantly improved the goodness of fit of linear and logistic models of non-stationary noise acceptability containing Loudness and Sharpness.

A new noise metric has been developed that may be used for optimization problems involving aerodynamic noise from a clean wing. The modeling approach uses a classical trailing edge noise theory as the starting point. The final form of the noise metric includes characteristic velocity and length scales that are obtained from three-dimensional, steady, RANS simulations with a two- equation k-omega turbulence model. The noise metric is not the absolute value of the noise intensity, but an accurate relative noise measure as shown in the validation studies. One of the unique features of the new noise metric is the modeling of the length scale, which is directly related to the turbulent structure of the flow at the trailing edge. The proposed noise metric model has been formulated so that it can capture the effect of different design variables on the clean wing airframe noise such as the aircraft speed, lift coefficient, and wing geometry. It can also capture three-dimensional effects which become important at high lift coefficients, since the characteristic velocity and the length scales are allowed to vary along the span of the wing. Noise metric validation was performed with seven test cases that were selected from a two-dimensional NACA 0012 experimental database. The agreement between the experiment and the predictions obtained with the new noise metric was very good at various speeds, angles of attack, and Reynolds Number, which showed that the noise metric is capable of capturing the variations in the trailing edge noise as a relative noise measure when different flow conditions and parameters are changed. Parametric studies were performed to investigate the effect of different design variables on the noise metric. Two-dimensional parametric studies were done using two symmetric NACA four-digit airfoils (NACA 0012 and NACA 0009) and two supercritical (SC(2)-0710 and SC(2)-0714) airfoils. The three-dimensional studies were performed with two versions of a conventional transport wing at realistic approach conditions. The twist distribution of the baseline wing was changed to obtain a modified wing which was used to investigate the effect of the twist on the trailing edge noise. An example study with NACA 0012 and NACA 0009 airfoils demonstrated a reduction in the trailing edge noise by decreasing the thickness ratio and the lift coefficient, while increasing the chord length to keep the same lift at a constant speed. Both two- and three-dimensional studies demonstrated that the trailing edge noise remains almost constant at low lift coefficients and gets larger at higher lift values. The increase in the noise metric can be dramatic when there is separation on the wing. Three-dimensional effects observed in the wing cases indicate the importance of calculating the noise metric with a characteristic velocity and length scale that vary along the span. The twist change does not have a significant effect on the noise at low lift coefficients, however it may give significant noise reduction at higher lift values. The results obtained in this study show the importance of the lift coefficient on the airframe noise of a clean wing and favors having a larger wing area to reduce the lift coefficient for minimizing the noise. The results also point to the fact that the noise reduction studies should be performed in a multidisciplinary design and optimization framework, since many of the parameters that change the trailing edge noise also affect the other aircraft design requirements. It's hoped that the noise metric developed here can aid in such multidisciplinary design and optimization studies. / Ph. D.

No / The paper describes model testing of the acoustic performance of vertically louvred and the corresponding predicted performance using a modified Boundary Element Method (BEM) program. The program was developed in a previous phase of the Transport Research Laboratory's research into the performance of modified barriers. Measurements on 1/20th scale model barriers were carried out in a semi-anechoic chamber designed primarily for scale model experiments to investigate outdoor sound propagation under controlled conditions. It was concluded from measurements in the scale model facility that the modified BEM code provided an adequate description of the leakage of sound through louvred barriers. The program was subsequently used to examine the performance of various designs of barrier in order to identify likely cost effective designs.