Abstract The advances of modern technology , creating a CPU and hardware speed greatly enhance the relative increase in number of work- ing temperature , so as not to make parts for high temperature, shortened life expectancy , we must take active cooling can be resolved , is gener- ated by the use of forced convection fan the heat away , but the fan noise when running , although not damage the hearing , have the potential to affect users of emotions ; as people increasingly rely on the computer, the fan gradually pay attention to the noise problem , so fans of R & D in recent years , in addition to increasing thermal efficiency , the increasing demands for noise. This article will examine the main centrifugal fan to AIO computer system for the experiment; AIO computer is the host and screen into one of the computer system, characterized by the internal space is small, heat is not easy, so the general would choose as the main centrifugal fan cooling fan, but the disadvantage of centrifugal fan noise is high, so this will do for the improvement of centrifugal fan noise research; to change the location of support ribs as the experimental setting, experimental method consists of three steps; first: Analog and down air inlet differences in velocity distribution, the second: the actual measurement centrifugal fan, is divided into single and measurement noise into the system and the sound quality of the judge, the third: performance testing; study showed that support rib in the middle of the design, the noise about 10% area reduction, sound quality also improved the effectiveness of nearly 50%, performance is also about 10% of the upgrade, the support rib in the middle of the design for double inlet centrifugal fans, for the better design.

No description available.

Sound quality analysis is a tool designed to help determine customer preferences, which can be used to help the designer improve product quality. Many industries desire to know how the consuming public perceives their product, as this affects the product life and success. This research investigates which of the six sewing machines provided by Viking Sewing Machine Group (VSM group) consumers find most acoustically appealing. The sound quality analysis methods used include both jury based listening tests and quantitative sound quality metrics from empirical equations. The results from both methods are completely independent and are shown to have a very strong correlation. The procedures and results of both methods, jury listening tests and mathematical metrics, are presented. Near field sound intensity scans identified acoustic hot spots and give direction for possible design modifications to improve the acoustic signature of the two top tier machines, the Designer 1 and Creative 2144 (Husqvarna Viking and Pfaff respectively). This research determined that the entry level Pfaff Select 1530 has the most acoustically appealing sound of the six machines evaluated. In addition, it was also determined that a reduction in the higher frequency sounds produced by the machines is preferred over a reduction in the lower frequency sounds. Further investigations, including an evaluation of machine isolation and startup sounds, were also performed. The machine isolation results are highly dependant on the individual machine being evaluated and would require independent evaluation. In the machine startup sound assessment, it was discovered that again the Pfaff Select 1530 has the preferred sound. Near field acoustic intensity scans provide additional information on locations of strong acoustic radiation. The near field scans provided valuable design information. The acoustic "hot" spots were discovered to exist in the lower portions of the machines near the main stepper motor in the Designer 1, and radiating from the bottom plate of the machine in the Pfaff Creative 2144. This analysis has led to various design modifications that could be implemented to improve the sound quality of the machines, specifically the Designer 1 and the Creative 2144.

No description available.

While a limited body of research pertaining to vocal sound quality exists, technological advances in sound analyses have facilitated a reexamination of vocal timbre. The sound quality of sung vowels ([ a], [e ], C i ]) produced by ten baritone/bass singers at the University of North Texas was analyzed by the use of Fourier analysis and electronic digital equipment. This procedure and equipment produced results over a wider frequency range with greater accuracy than prior studies on vocal timbre. The study sought to answer the following questions: (1) Using formant regions between 0-20 kHz for comparison, what similarities and differences can be observed among spectra produced from [a], [e], and [ i ] vowels sung by baritone/bass singers? (2) Using formant regions between 0-20 kHz for comparison, what similarities and differences can be observed among spectra produced from [a], [ e ], and [ i ] vowels sung by baritone/bass singers with regard to individual singers? (3) Approximately what vocal-tract tube lengths were used by baritone/bass singers when performing [a], [e ], and [ i ] vowels? (4) What similarities in vocal-tract tube lengths can be generalized as to [ a], L e ], and [ i ] vowels sung by individual baritone/bass singers? The results of the study suggested that: (1) Below approximately 4 kHz formant frequency location can be generalized by a specific vowel between subjects. (2) Above 4 kHz the generalization of formant frequency location is difficult between subjects singing the same vowels, but general frequency location for formants can be identified between samples produced by the same singer performing different vowels. (3) Subjects did alter their vocal-tract lengths as different vowel sounds were performed, but no overall pattern of tube length with reference to specific vowels was indicated. (4) Each singer did use a unique vocal-tract length. The average estimated vocal-tract length for all subjects singing a specific vowel revealed little variation in tube length with an average tube length of 278.97 mm.

La caractérisation du ressenti global du bruit intérieur d’habitacle passe par la définition des conditions conduisant à l’audibilité de ces composantes fréquentielles, émergeant du bruit de fond. Mon travail de thèse s’est attaché à décomposer les situations de masquage pouvant apparaître au sein d’automobile ou de train, en complexifiant progressivement les stimuli au cours des mesures de masquage, en laboratoire. Un certain nombre de choix méthodologiques ont dû être effectués, limitant l’étude aux sons stationnaires, sans modulation d’amplitude, sans déphasage entre les oreilles.Nous nous sommes confrontés tout d’abord à la question du mode de reproduction. Nous avons souligné les difficultés rencontrées lors de la mesure de l’étalonnage des casques d’écoute. Nous avons validé l’écoute au casque étalonné au tympan, en comparant les mesures de seuils masqués de sons purs dans un bruit large bande, à une écoute en chambre sourde, face à une enceinte monophonique.Ensuite, nous avons complexifié le contenu spectral du masque en présentant des bruits comportant des tonalités marquées. Plusieurs modèles perceptifs ont été testés de façon à prédire l’élévation des seuils mesurés.Enfin, nous avons étudié l’amélioration à la détection d’un signal multifréquentiel et développé un modèle, issu de la théorie de la détection du signal, applicable aux signaux présentant des différences en niveau entre les composantes. L’influence du bruit masquant a également été révélé par la mesure de seuils de signaux multifréquentiels dans un bruit d’habitacle automobile. Un unique modèle de détection de signaux émergents, applicable aux signaux stationnaires, a été proposé. Ces travaux ouvrent de nombreuses perspectives, comme la poursuite du travail sur les émergences multifréquentielles, la prise en compte de la relation de phase entre les oreilles, l'étude des sons non stationnaires ou les phénomènes attentionels. / Emergences like tonal components take part in automobile and railroad acoustic comfort. These signals are totally or partially masked by the background noise, of automobile or train coaches. Determining the audibility of spectrally complex signals in a complex broadband noise masker, with tonalities or not, is yet an unanswered question and an industry expectation to characterize the overall sound quality of train/car cabins. The purpose of my PhD thesis was to measure detection thresholds for tones or complex tones, masked by a broadband noise, with pronounced tonal components or not. Several choices must have been performed, restricting study to stationary sounds, without modulation of amplitude, without inter-aural phase differences.First, different methods of sound reproduction are compared measuring detection thresholds. We underlined difficulties met during the measure of the calibration of headphones We validated the eardrum calibration, by comparing detection thresholds of pure sounds in a broad band noise, in a anechoic room, in front of a monophonic loudspeaker.Then, the masking thresholds of pure tones in the presence of maskers with pronounced tonal components are measured. Several perceptual models were tested in order to predict the elevation of the measured thresholds.Finally, we studied the improvement in detection of a multitone complex and developed a model to predict masking thresholds, based on the statistical summation model, applicable to multicomponent signals with differences in level between components. The influence of tonalities have been revealed with the car cabin noise.A threshold model, applicable to the stationary sounds, is proposed. Several perspectives are discussed, from time-variant signals to inter-aural differences or attention phenomena for example.

Les constructeurs se préoccupent de plus en plus du bruit généré par leurs produits, que ce soit dans le domaine de l’automobile, de l’aéronautique ou récemment de l’électroménager, à cause des réglementations beaucoup plus strictes en termes de niveau sonore. Mais au-delà du bruit, la demande des utilisateurs ou de la population, concerne encore davantage la qualité sonore.Dans l’équipement électroménager, la chaudière hybride innovante développée par e.l.m. leblanc est un produit très intéressant sur le plan énergétique, puisqu’à la chaudière à gaz à condensation est associée une pompe à chaleur dans un encombrement réduit. Cette dernière a un coefficient de performance de 3,7 (3,7 kW/h fourni pour une consommation d’1kW/h électrique), elle permet ainsi une grande économie sur la facture de l’utilisateur.Cependant, son niveau sonore élevé empêche son installation dans des pièces de vie, comme la cuisine, limitant ainsi la conquête d’un plus vaste marché. Il faudrait que son bruit soit environ 40 fois moins fort pour répondre au niveau réglementaire. La conception d’une nouvelle génération de chaudière hybride a été l’occasion de lancer cette étude visant non seulement à réduire le niveau sonore, mais également à sculpter le son, afin de le rendre moins gênant.Une nouvelle approche, appelée Acoustique Prévisionnelle des SYstèmes Dynamiques (APSYD), a été utilisée et a servi de fil conducteur à notre étude. Elle permet de prendre en compte les critères acoustiques, vibratoires et également ceux de la qualité sonore, très en amont dans la conception d’un produit, ce qui évite de coûteuses modifications, ou même le rejet du produit fini, s’il est jugé trop bruyant.Dans ce travail de thèse, des mesures acoustiques et vibratoires sur les chaudières hybrides existantes ont été réalisées et analysées pour identifier les modifications optimales susceptibles de diminuer le bruit. Des solutions ont été proposées et leurs effets ont été évalués par des mesures. Le niveau sonore réglementaire a été atteint avec les dispositions que nous avons proposées.Pour intégrer la composante qualité sonore dans la conception, des tests d’écoute ont été réalisés pour identifier la cible sonore de la nouvelle chaudière hybride. Des analyses statistiques (ACP, AFC, ANOVA) ont permis de faire ressortir les paramètres qui interviennent, parfois de manière très fine, sur le ressenti sonore. Nous avons également testé l’effet de l’insertion d’une sonorité musicale et nous avons trouvé une corrélation entre l’agrément du bruit de l’appareil et ce paramètre.Ce constat a orienté la thèse vers le développement d’une méthode originale permettant de définir les paramètres physiques d’un ventilateur pour qu’il génère une sonorité musicale donnée. Pour cela, nous avons proposé une nouvelle démarche semi-expérimentale permettant de prédire le spectre de raies d’une roue, et employé un algorithme d’optimisation, afin de rechercher les paramètres géométriques optimaux de la roue. Elle a été validée sur deux bancs d’expérimentation. Cette nouvelle méthode permet de sculpter le son tonal d’un ventilateur, d’une turbomachine, ou plus largement d’une machine tournante. / Manufacturers increasingly care about noise made by their products, whether it is in car, in aeronautics, or recently in home appliances industry, because of much more restricting regulations regarding noise level. But beyond noise, users and population’s demand concerns more about sound quality.Among domestic equipment, the innovate hybrid boiler developed by e.l.m. leblanc is an interesting product energetically speaking as the condensing gas boiler is combined with a heat pump in a limited space. The performance coefficient of the heat pump is 3.7 (3.7 kW/h provided for an electric consumption of 1 kW/h), resulting in large savings on users’ bills.However, its high noise level prevents its installation in living spaces, such as kitchen, restricting the conquest of a larger market. His noise should be 40 times lower to meet regulatory level. The design of a new generation of hybrid boiler has been the opportunity to start this study aiming not only to reduce noise level, but also to carve sound in order to make it less annoying.A new approach, called Projected Acoustics of Dynamic Systems (PADS), has been used and has acted as a thread for our study. It takes into account acoustic, vibrating criteria and also those from sound quality well upstream from product design stage, thus avoiding expensive modifications or even rejection of the finished product if the latter is considered noisy.Acoustic and vibration measurements have been carried out on existing hybrid boilers and they have been analyzed in order to identify optimal modifications that may reduce noise. Solutions have been suggested and their effects have been evaluated by measurements. The regulatory noise level is reached with suggested measures.To integrate sound quality component into design, listening tests have been carried out to identify the sound target of the new hybrid boiler. Statistical analysis (PCA, FCA, Variance Analysis) brought out parameters impacting on noise perception, sometimes very subtly. We have tested the effect of the integration of musical tone and a correlation between noise pleasantness and this parameter was observed.This observation has concentrated this thesis on the development of an original method that can define the physical parameters of a fan so it makes a given musical tone. To do so, we have suggested a new semi-experimental approach that can predict line spectrum of a fan and we have used an optimization algorithm in order to find the optimum geometrical parameters. This new method has been validated with two test benches. It can be used to curve tonal noise of a fan, a turbomachine, or more generally a rotating machine.

A crescente demanda por reduções nos níveis de ruído gerados por veículos, e, mais recentemente, pela melhoria na qualidade sonora, aliada às penalidades associadas ao espaço e peso das soluções passivas, sugerem o uso de técnicas de controle ativo de ruído. O projeto de sistemas ativos deve fazer parte do desenvolvimento de produto desde sua fase de concepção para que tais soluções sejam aplicadas em nível industrial. Portanto, propõem-se metodologias de simulação para o projeto de sistemas de controle de ruído. Modelos vibroacústicos em elementos finitos são reduzidos e formulados em espaço de estados para permitir a simulação do sistema em malha fechada. Os modelos envolvidos permitem a inclusão da dinâmica de sensores e atuadores para que o desempenho seja previsto de forma acurada. As vantagens do uso de simulação de sistema de controle de ruído, além da redução de custo e tempo de projeto, permite o desenvolvimento de sistemas ativos onde estrutura e controle são desenvolvidos de forma simultânea. O procedimento de simulação é validado experimentalmente, tanto para malha aberta quanto para malha fechada, com o uso de uma geometria simplificada de veículo. Graças à redução dos modelos originais, é possível utilizar técnicas de otimização, onde a interação entre a estrutura e o controle são considerados de forma simultânea, resultando em um sistema ativo com desempenho superior a sistemas desenvolvidos separadamente. Através dos resultados obtidos com a otimização observam-se os parâmetros conflitantes e as decisões de compromisso envolvendo o controle de transmissão de ruído em veículos. Demonstra-se, que um sistema de controle estrutural, descentralizado, de alimentação de velocidade, oferece praticidade de implementação e desempenho satisfatório. Finalmente, o impacto do controle ativo na percepção dos ocupantes é avaliado por meio de métricas objetivas de qualidade sonora, como tonalidade e nível de pressão sonora. / The demands for improvement in sound quality and noise reduction generated by vehicles are steadily increasing, as are the penalties for space and weight of passive control solutions. This scenario suggests the use of active noise control. In order to bring active solutions to industrial level applications, the design of such systems should be part of the product development cycle. Therefore, methodologies for simulating and designing such active solutions are proposed. These models should allow the inclusion of sensors and actuators models, if accurate performance indexes are to be accessed. The challenge thus resides in deriving reasonable sized models that integrate structural, acoustical, and even sensor/actuator models in the controller algorithm simulation. The proposed modelling procedure coupe with this challenge, and besides the advantages on the cost and time reduction in the development phase, it allows the development of active systems with structure and controllers being designed concurrently. An experimental validation is performed using data obtained from simplified car geometry. Thanks to the reduced models, it is possible to run optimization routines in which the interaction of structure and control is considered, thus resulting in an improved system when compared to conventional stepwise procedure. The optimization results presented give some insights on the problem of designing active noise controllers for transmission loss in vehicles. It is shown that, a purely structural decentralized velocity feedback controller can offer both, easy practical implementation and satisfactory noise reduction. Also, the impact of the active control on the perceived noise reduction is evaluated with objective sound quality metrics, such as sound pressure level and specific loudness.

A crescente demanda por reduções nos níveis de ruído gerados por veículos, e, mais recentemente, pela melhoria na qualidade sonora, aliada às penalidades associadas ao espaço e peso das soluções passivas, sugerem o uso de técnicas de controle ativo de ruído. O projeto de sistemas ativos deve fazer parte do desenvolvimento de produto desde sua fase de concepção para que tais soluções sejam aplicadas em nível industrial. Portanto, propõem-se metodologias de simulação para o projeto de sistemas de controle de ruído. Modelos vibroacústicos em elementos finitos são reduzidos e formulados em espaço de estados para permitir a simulação do sistema em malha fechada. Os modelos envolvidos permitem a inclusão da dinâmica de sensores e atuadores para que o desempenho seja previsto de forma acurada. As vantagens do uso de simulação de sistema de controle de ruído, além da redução de custo e tempo de projeto, permite o desenvolvimento de sistemas ativos onde estrutura e controle são desenvolvidos de forma simultânea. O procedimento de simulação é validado experimentalmente, tanto para malha aberta quanto para malha fechada, com o uso de uma geometria simplificada de veículo. Graças à redução dos modelos originais, é possível utilizar técnicas de otimização, onde a interação entre a estrutura e o controle são considerados de forma simultânea, resultando em um sistema ativo com desempenho superior a sistemas desenvolvidos separadamente. Através dos resultados obtidos com a otimização observam-se os parâmetros conflitantes e as decisões de compromisso envolvendo o controle de transmissão de ruído em veículos. Demonstra-se, que um sistema de controle estrutural, descentralizado, de alimentação de velocidade, oferece praticidade de implementação e desempenho satisfatório. Finalmente, o impacto do controle ativo na percepção dos ocupantes é avaliado por meio de métricas objetivas de qualidade sonora, como tonalidade e nível de pressão sonora. / The demands for improvement in sound quality and noise reduction generated by vehicles are steadily increasing, as are the penalties for space and weight of passive control solutions. This scenario suggests the use of active noise control. In order to bring active solutions to industrial level applications, the design of such systems should be part of the product development cycle. Therefore, methodologies for simulating and designing such active solutions are proposed. These models should allow the inclusion of sensors and actuators models, if accurate performance indexes are to be accessed. The challenge thus resides in deriving reasonable sized models that integrate structural, acoustical, and even sensor/actuator models in the controller algorithm simulation. The proposed modelling procedure coupe with this challenge, and besides the advantages on the cost and time reduction in the development phase, it allows the development of active systems with structure and controllers being designed concurrently. An experimental validation is performed using data obtained from simplified car geometry. Thanks to the reduced models, it is possible to run optimization routines in which the interaction of structure and control is considered, thus resulting in an improved system when compared to conventional stepwise procedure. The optimization results presented give some insights on the problem of designing active noise controllers for transmission loss in vehicles. It is shown that, a purely structural decentralized velocity feedback controller can offer both, easy practical implementation and satisfactory noise reduction. Also, the impact of the active control on the perceived noise reduction is evaluated with objective sound quality metrics, such as sound pressure level and specific loudness.

No description available.