Showing papers in "Noise & Vibration Worldwide in 2006"

Prediction and Analysis of Blast Parameters Using Artificial Neural Network

Abstract: In this study an attempt is made to predict the ratio of muck pile profile before and after the blast, fly rock and total explosive used, based on simple field tests as well blast design parameters. Prediction is done by making three different artificial neural network (ANN) models. Comparative statistical analysis is made among these three networks to ensure their performance suitability. Models of ANN were based on Feed Forward Back Propagation network with training functions – Resilient Backpropagation, One Step Secant and Powell-Beale Restarts. Total numbers of datasets chosen were 92 among which 17 were chosen for testing and validation and the rest were used for the training of networks. Statistical analysis is also made for these datasets. Considering performance for all the outputs, the best results are predicted by Powell-Beale Restarts, with an average percentage error of 5.871% for the ratio of muck pile before and after the blast, 5.335% for fly rocks and 5.775% for total explosive used. These...

Analytical Investigation on the Effect of Gear Teeth Faults on the Dynamic Response of a Planetary Gear Set

Abstract: Due to excessive service load, inappropriate operating conditions or simply end of life fatigue, damage can occur in gears. When a fault, either distributed or localised, is incurred by gears, the stiffness and consequently vibration characteristics of the damaged tooth will change. In this work an analytical formulation of the time varying geannesh stiffness was derived. Two local tooth faults are modelled: tooth pitting and crack. Their influence on the gearmesh stiffness is analysed. A planetary gear set is presented as a case study to implement the tooth fault modelling. The response shows amplitude modulation resulting in high activity of sidebands.

Noise, stress and annoyance

Abstract: The effects of sound on man are reviewed with emphasis on the physiological reaction mechanisms and the ultimate stress reaction. It is seen that energy related noise levels are poor predictors for the reactions in man as noise is always interpreted in the central nervous system, generating secondary and tertiary reactions that are not controlled by the brain cortex. The stimulation of these reaction pathways in acute situations lead to involuntary reflexes and feelings of fright and despair. In chronic exposure situations a give-up stage may develop with reduced corporal and mental functions. In the acoustical panorama peak level noises usually cause the most pronounced effects as they stimulate reactions of fear and flight. The practical consequences of these reaction patterns in terms of prevention are discussed.

An Acoustic Window System with Optimum Ventilation and Daylighting Performance

Abstract: The paper presents a series of theoretical, experimental and numerical studies on using transparent micro-perforated absorbers in a window system to allow noise attenuation whilst at the same time maintaining ventilation for comfort and daylighting. The underlying theory for micro-perforated absorbers and the application in silencers is examined. Experimental results between a semi-anechoic chamber and a reverberant chamber using a standard window mock-up are presented. Numerical simulation using finite element method is summarised, considering the effects of opening size, air gap, louvers, hood, and absorbers. It is shown that such a window system can perform better than closed single glazed windows, while still allowing for significantly more ventilation for comfort than most current systems as well as for high levels of light ingress.

Significance of Vibration Diagnosis of Rotating Machines during Installation and Commissioning: A Summary of Few Cases

Abstract: Satisfactory operation of any machine is always important for plant safety, increased productivity, and low downtime and maintenance overhead. Such requirements could usually be fulfilled by proper design and installation of machines at site. The design part is perhaps more mature in most cases, however installation may play a significant role in the dynamic behaviour even for properly designed machines. Vibration based condition monitoring and codes are well known and widely followed for most of the conventional rotating machines like pumps, motors, turbines, etc. However many rotating machines often used in different process and power plants are not of conventional type wherein condition monitoring is also important, but the codes and the diagnostic techniques may not directly be applicable. The vibration measurements and analysis during commissioning is important to resolve the problems related to the machine installation, if any, and identify the parameters for future condition monitoring of different...

Portable diamond cutter for sawing Kotah Stone – a case study on its noise emission and control

Abstract: With increasing awareness of the need for quieter operation of industrial machines, much effort has been put into reducing the emitted noise levels in their design, development and operation stages. This study characterizes emitted noise from Jhiri machines as well as suggesting suitable control measures to be incorporated for noise abatement.

Multi-mode shunt damping of piezoelectric smart panel for noise reduction

Abstract: A piezoelectric smart panel is a plate structure on which a piezoelectric patch is attached with an electrical shunt circuit. When a sound is impinged on the panel structure, the structure vibrates and the attached piezoelectric patch produces an electrical energy, which can be effectively absorbed by the electrical shunt circuit. Since the energy absorption strongly depends on the vibration mode of the panel structure, many patches are required for broadband noise reduction. Thus, we report a multi-mode shunt damping of a smart panel by using a single piezoelectric patch in conjunction with a blocked shunt circuit. Modeling, shunt parameter tuning and implementation of the blocked shunt circuit along with an acoustic test of the panel are explained. A remarkable reduction of the transmitted noise was achieved for multiple modes of the panel. Since this technology has merits in terms of compactness, low cost, robustness and easiness to install, practical applications in many noise problems can be anticipated.

Hybrid Passive-Active Absorption of Broadband Noise Using MPPs:

Abstract: Passive materials provide sound absorption in a frequency band whose low frequency limit depends on its thickness. In general, sound absorption in the lower frequency range requires such bulky materials that the passive solution becomes impractical, except for special installations, such as anechoic chambers. On the other hand, active systems allow control of the input impedance of multilayer absorbers, affording low frequency absorption. When the properties of the passive system are properly combined with the active controller, it is possible to design broadband sound absorbers with an absorption coefficient close to unity from 100 Hz. These systems are named hybrid passive-active absorbers. This paper describes the implementation of such a hybrid absorber, using a microperforated panel (MPP) as the passive material.

Prediction of Safe Charge to Control Ground Vibration in Surface Mining

Abstract: Many researchers have proposed various predictor equations to determine the PPV (Peak particle velocity) which is the function of distance and maximum safe charge per delay. When the maximum safe charge per delay is calculated by different predictors its values vary because these predictors are formulated on different bases with limited observations. In this paper, an equation has been proposed for estimation of the maximum safe charge per delay and its performance has been compared with other predictors. The proposed predictor is the function of PPV and distance. Results were well correlated and near to the observed value. The maximum charge per delay has been calculated by all predictors and compared with the proposed one. The coefficient of correlation was found to be high for the proposed predictor. This may be give better prediction of safe charge as compared to other predictors for different rock litho units.

Vibration monitoring for local tooth damage in multistage gearboxes

Abstract: An adaptive approach was applied for local tooth damage diagnostics in gearboxes. The expediency of adaptation was proved experimentally for the new diagnostic feature, the sum of normalized sideband amplitudes. The positive correlation between mesh amplitudes and their sideband amplitudes was found experimentally for the first time.Novel adaptive vibration condition monitoring technology for local tooth damage in gearboxes was developed and experimentally validated.The experimental results showed an increase in effectiveness of the diagnostics when the adaptive technology was used.

Active local control of propeller-aircraft run-up noise

Abstract: Engine run-ups are part of the regular maintenance schedule at airports. The noise generated by the run-ups propagates into neighbouring communities, disturbing the residents. Active noise control is a potentially cost-effective alternative to passive methods, such as enclosures. Propeller aircraft generate low-frequency tonal noise that is highly compatible with active control. This paper presents a preliminary investigation of the feasibility and effectiveness of controlling run up noise from propeller aircraft using local active control. Computer simulations for different configurations of multi-channel active-noise-control systems, aimed at reducing run-up noise in adjacent residential areas using a local-control strategy, were performed. The variations of the attenuation and amplification zones with the number of control channels, and with the source/control-system geometry, were studied. The aircraft was modeled using one or two sources, with monopole or multipole radiation patters. Both free-field ...

Acoustic Detection of Buried Landmines Using Pulsed ESPI

Abstract: Acoustic methods of landmine detection have demonstrated promising results in detecting buried landmines in laboratory and field tests They are based on generation of vibrations of the ground and measurement of the vibration response of the ground over the area of interest A buried landmine can be detected by analyzing spatial distribution of the ground vibration Reliable detection of mines requires fast measurement of vibration with high spatial resolution This work studies the application of a pulsed electronic speckle pattern interferometer (ESPI) for the vibration measurement of the ground surface in acoustic landmine detection Experimental results are presented from laboratory experiments The effect of the vibration of unconsolidated soil on the speckle decorrelation is discussed Results show that pulse ESPI can create a spatial map of vibrating ground in a time equal to or shorter than a half a period of vibration and have the ability to detect buried landmines

On the annoyance caused by magnetic levitation train passby sounds

Abstract: In a laboratory study, the annoyance caused by the passby sounds from a magnetic levitation (maglev) train was investigated. The listeners were presented with various sound fragments. The task of the listeners was to respond after each presentation to the question: "How annoying would you find the sound in the preceding period if you were exposed to it at home on a regular basis?" The independent variables were a) the driving speed of the maglev train (varying from 100 to 400 km/h), b) the outdoor A-weighted sound exposure level (ASEL) of the passbys (varying from 65 to 90 dB), and c) the simulated outdoor-to-indoor reduction in sound level (windows open or windows closed). As references to the passby sounds from the maglev train (type Transrapid 08), sounds from road traffic (passenger cars and trucks) and more conventional railway (intercity trains) were included for rating too. Four important results were obtained. Provided that the outdoor ASELs were the same, 1) the annoyance was independent of the d...

Noise Indices for Assessing Domestic Air Conditioner Noise

Abstract: In the present study, a survey was carried out to examine the capabilities of various noise indices for describing the nuisance caused by exposure to air conditioner noise inside residential apartments. Physical noise measurements were also carried out. Results show that the Zwicker's loudness level and the percentile level of 90% exceedence are the two major indices for air conditioner noise assessment. The rating level appears not to be a good indicator for such a purpose.

Collaboration grids: virtual products and business benefits

Abstract: have been pushing hard to make progress. Intel, IBM, Nokia and other firms with large numbers of designers want their design groups to use a collaborative environment so designers in different locations can work as a single team. Auto firms and aerospace companies have also been facing the issue of collaboration, largely because they need to reduce the time-to-market for new products (note the disastrous consequences in the Airbus case!). Recent and forthcoming meetings of European Commission-funded projects (e.g., SIMDAT, VIVACE) and of service-oriented architecture (SOA) product firms (e.g., the MSC Software conferences on virtual product development) indicate that auto and aerospace firms have made real progress. Using commercial SOA products or tools and grids, they have created “virtual cars” and “virtual planes,” 3-D files with data that support collaboration between engineering design groups. The virtual cars test designs and manage the inclusion of crash, computational fluid dynamics (CFD), structural testing, and noise-vibration and harshness modeling in the overall model of a car. The advantages of using “virtual cars” are several. First, firms can go through many more static and dynamic simulations using well-known tools such as LS Dyna, NASTRAN, etc., for crash and CFD analysis. This provides robust results and shortens timeto-market. Second, testing and design costs are reduced because simulations replace much of the work that used to be done in these groups. This not only reduces costs, but also cuts down what had been a major area in product development. Third, auto firms are looking for more flexibility in design. They need to be able to respond quickly to new regulations, such as German requirements that the front ends of cars create fewer significant injuries to pedestrians. Virtual cars have let manufacturers change a model design quickly. Fourth, virtual cars have let companies such as Audi greatly increase the number of models they offer. They can design different versions that build on the same frame and often retain other parts of an established design, such as the windows, doors or trunk. Audi now markets about 40 models compared to about six a decade ago. To create virtual cars, auto firms have enlarged their grids to more than 1,000 CPUs. They have employed traditional applications as part of their SOAs, and employ many simulation and CAE applications on SOAs. Having excellent access to needed data, as well as to compute power, is a sine qua non for virtual cars. At the present time, virtual cars are developed at a single simulation and design facility. Because virtual car files are often at the 10 terabit level, firms have begun to expand the capacities of their campus WANs. In the future, they plan to link distant design centers together. Design engineers at Audi in Ingolstadt, Germany, will work with their counterparts at SEAT in Martorell, Spain, on the same “virtual car.” Engineering groups, such as Berco, that do undercarriage parts subcontracting may also be linked to the Audi network to collaborate in engineering design. This sharing will require high-speed networks with capacities well beyond the 10-20 Mbps now used to communicate with partners. Dark fiber is one way to put these connections in place. However, not all auto firms have been moving in this direction. Some have had difficulty using virtual cars. In some cases, this is because there is a true divide among big auto firms. Some have focused on lean manufacturing, almost to the exclusion of what might be called “lean” engineering (i.e., flexible and visually beautiful design that also greatly shortens product development time and reduces development costs). In some auto firms that don’t use the tools SOA software firms have chosen to support “virtual cars,” they have found it a very great challenge to use this innovation. It remains to be seen whether they will continue to resist changing their design operations or if “lean manufacturing” [creating the greatest efficiencies in manufacturing] will trump “lean design.” Initial interviews suggest that it might not be possible to compete in global auto markets unless you combine “lean manufacturing” with “lean design” by using virtual cars. COLLABORATION GRIDS: VIRTUAL PRODUCTS AND BUSINESS BENEFITS

Performance Analysis of an Active Noise Cancellation Hearing Protector

Abstract: When designing an active noise cancellation hearing protector, it is relatively easy to implement a laboratory prototype with high performance. However, when the device is taken out of the laboratory into real extremely noisy situations, it must be capable of producing very high sound pressure levels. In this paper, the factors, which limit the low frequency performance and dynamic range are analysed. The results show that the voltage swing of the loudspeaker amplifier and the force factor of the loudspeaker are two important limiting factors in extremely loud situations. A prototype of an active noise cancellation hearing protector was implemented and its performance was measured in an authentic noisy situation. The developed device attenuated 125 Hz tonal noise by 18 dB. The active noise cancellation system attenuated noise even at a sound pressure level of 118 dB SPL. This can be considered sufficient for most situations.

Analytical and Experimental Study on Noise Attenuation of Multi-Cylinder Diesel Engine with Existing and Modified Muffler

Abstract: Man's desire for a pollution free atmosphere entails control of air pollution and noise pollution. The principal sources of noise in automotive engines are intake noise, radiator noise, combustion noise, exhaust noise etc. Out of these, exhaust noise is predominant and has to be controlled. Noise pollution affects human beings physiologically and psychologically.In this paper on reactive muffler for a multi-cylinder diesel engine is designed and modified. More attenuation is given by making some changes in its configuration.The Bond graph technique has been applied for the analytical results of the muffler. The modelling of acoustic and other systems are easily and logically achieved through Bond graph technique[1,2,3]. Bond graph, invented by Paynter, is a method or representation of a physical system by means of symbols and lines, identifying power flow paths and lumped parameter elements of resistance, capacitance and inductance.The Bond graph model is created by taking wave propagation in acoustic mat...