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Ultrasonic noise is on the list of harmful factors in thework environment in many countries. In the frequency range above 20kHz there is a shortage of clear and complete information about the factors affecting the measurement results of sound pressure level. Until recently, the ultrasonic noise measurement methods and determining the uncertainty of measurements were combined with audible noise measurement methods (ISO9612:1997). Currently there are no up-to-date internationalstandardsforthemeasurementofultrasonicnoiseinthework- place.ThearticledescribestheapplicabilityoftheselectedpointsoftheISO 9612:2009 standard in the measurement of ultrasonic noise and attention was drawn to items that are not full yexamined. [ABSTRACT FROM AUTHOR]

The paper describes the in situ testing of the developed and designed acoustic control systems to track an air percussion machine movement in soil. Based on the test data processing, the authors have related the acoustic signal due to machine motion and the machine location. It is concluded advisable to control air percussion machinery movement in soil using acoustic signals. [ABSTRACT FROM AUTHOR]

Abstract: The key of the signal processing is obtaining the useful signal from the noise environment. In this paper, a novel noise cancellation system is designed by the RBF neural network, does not need the previous information of input signal and noise, overcomes some inherent shortcomings of the non-Gauss noise processing in the traditional linear filter, and has better ability of nonlinear mapping and self-learning. It is shown that the system has good performance in noise processing by the Matlab simulation. [Copyright &y& Elsevier]

This paper presents a method based on the Kirchhoff diffraction theory to predict the shielding of turbo machinery noise by the airframe of an advanced aircraft configuration. The key feature of this method is the fast computational time, even at very high frequencies, which makes it a useful tool to rapidly assess the noise footprint of an aircraft design. The offline part preprocesses the three-dimensional shielding geometry into a contour of its outline based on the source line of sight. Given this contour, the online part calculates the noise attenuation at a particular observer location and source frequency and can be called multiple times by an aircraft noise prediction program to add shielding estimates to its effective perceived noise level calculations. This method is most accurate for flat shielding objects characterized by edge-diffraction rays, rather than smooth, rounded objects characterized by creeping rays; shielding differences of up to 3 dB were observed in calculations using a sphere and a disk. Finally, the method is applied to a hybrid wing-body aircraft to assess and quantify the noise shielding benefit of its large planform area. [ABSTRACT FROM AUTHOR]

In this paper, soft computing based system models were applied to predict opencast mining machineries noise. Noise is often regarded as a nuisance rather than as an occupational hazard in an opencast mining environment. Prolonged exposure to noise over a period of years generally causes permanent damage to the auditory nerve and=or its sensory components. To maintain the good working environment in mines, appropriate noise survey of machineries should be conducted. The measured sound pressure levels (SPL) for the equipments by sound measuring devices are considered inaccurate due to instrumental error, attenuation due to geometrical aberration, atmospheric attenuation etc. Some of the popular noise prediction models e.g. ISO-9613-2, CONCAWE, VDI and ENM have been applied in mining and allied industries to predict the machineries noise by cosidering all the attenuation factors. Mamdani, Takagi Sugeno Kang (T-S-K) fuzzy inference system and Adaptive Network based Fuzzy inference System (ANFIS) were used to predict the machinery noise in opencast mines. From the present investigations, it was observed that the ANFIS model gave better noise prediction than the Mamdani and TSK fuzzy. [ABSTRACT FROM AUTHOR]

The article discusses the variability or dynamics of generated noise in both frequency and time domains in relation to various independent variables related to coal extraction and transportation processes. The noise in an underground coal mine has components derived from continuous mining machines, roof bolters, and cars/vehicles used to transport personnel or coal. A noise data has been collected with the use of sound level meters and spectrum analysis .

The article discusses the use of experimental and simulation tests to determine the values of the global index of engine-generator. The development of global index machines aims to assess noise emitted by machines and to predict noise levels at workstations. Meanwhile, inversion method was used to determine sound power level.

Article covers the basics of practical applications, as well as the principles of construction of artificial neural networks. Also presents problems concerning traffic noise measurements conducted and the results of test measurements carried out in March 2011. [ABSTRACT FROM AUTHOR]

Systematic monitoring of noise levels was carried out inside the cabin of all the Heavy Earth Moving Machineries deployed in a chromite mining complex during summer 2008 and winter 2009. The present study aimed to estimate the significance and thedegree of association of the noise levels with respect to all the HEMMs. The analysis (t-test) shows that the equivalent noise (Leq) levels inside the cabin differ significantly with the test value of 85 dBA for all the HEMMs. Analysis of Variance reveals that the values of Leq are not identical with respect to the time of monitoring and also inside the cabins of different HEMMs (p<0.01). The Leq is the most significant during third part of time monitoring inside the cabin of the dozer (p<0.01). The Chi-square test reveals that 0.752 is the highest degree of association between the dozer, p=0.000(p<0.01) and Leq levels and exists a high degree of association. [ABSTRACT FROM AUTHOR]

In this paper, a new model-based Taylor series expansion error compensation (TSEEC) strategy is proposed to improve the contouring accuracy for computer numerically controlled (CNC) machines. In TSEEC, the contour error compensation problem is formulated as a Taylor series expansion problem, in which the value of the contour error is expanded around the reference points and the compensation components are calculated as the deviations from the reference points. Simulations show that, with perfect knowledge of the axial dynamics, zero contour errors can be achieved with TSEEC for both linear and circular contours. Due to modeling errors, external disturbances, and measurement noise, some modifications and experimentation need to be made to determine suitable parameters for implementation of the TSEEC scheme on a real machine. These measurements include a low-pass filter, a choice of a compensation target, and a compensation gain. Experimental results show the effectiveness of TSEEC in reducing contour errors and demonstrate the superiority of TSEEC over inverse feedforward compensation and cross-coupled control in improving the contouring accuracy. [ABSTRACT FROM AUTHOR]

"A type of machines" can be understood as a set of machines that have some part in common, and are generally used for the same function. Therefore, it seems logical to think that they should usually share the same working philosophy, which often includes a similar noise emission. This reasoning will be proved by the comparison of the different factors that characterize a machine, that is, the measurement of sound power level and sound quality. All of this should be done for a number of machines to guarantee enough heterogeneity in the test samples so as to probe the existence of a trend in the acoustical characteristics of the machines of the same family. This will lead to the existence of a sound pattern. It has been possible, for the panel saws family, to determine that emission pattern. The knowledge of this sound pattern offers a wide set of possibilities that permit emission reductions and protection of workers. [ABSTRACT FROM AUTHOR]

Functional link-based neural network models were applied to predict opencast mining machineries noise. The paper analyzes the prediction capabilities of functional link neural network based noise prediction models vis-`a-vis existing statistical models. In order to find the actual noise status in opencast mines, some of the popular noise prediction models, for example, ISO-9613-2, CONCAWE, VDI, and ENM, have been applied in mining and allied industries to predict the machineries noise by considering various attenuation factors. Functional link artificial neural network (FLANN), polynomial perceptron network (PPN), and Legendre neural network (LeNN) were used to predict the machinery noise in opencast mines. The case study is based on data collected from an opencast coal mine of Orissa, India. From the present investigations, it could be concluded that the FLANN model give better noise prediction than the PPN and LeNN model. [ABSTRACT FROM AUTHOR]

The object of this study is experimentally investigating pump noise and its relations with pressure fluctuations. Small size pump is tested in a semi-ancchoic chamber at different system conditions and different rotational pump speeds. Pump operational data, noise data and time dependent pressure data are recorded. Fast Fourier Transform spectra of noise and pressure data are compared. Coherence spectrum between sound pressure level and hydraulic pressures are obtained. The experiments have indicated that system characteristics such as geometric head do not have any influence on the noise of pump. On the other hand rotational speed which is a parameter of pump characteristics is distinguished on the sound spectra with peak frequencies proportional to the blade passing frequency of the pump. Results of cross correlations also show that, pump outlet pressure is a more significant source of noise than pump inlet pressure. [ABSTRACT FROM AUTHOR]

The identification/localization of propulsion noise in turbo machinery plays an important role in its design and in noise mitigation techniques. Nearfield acoustic holography (NAH) is the process by which all aspects of the sound field can be reconstructed based on sound pressure measurements in the nearfield. Efficient and accurate identification of noise sources, particularly in turbomachinery applications, is difficult due to complex noise generation mechanisms. A boundary element model which describes the transfer function between measurement data (acoustic pressure measurements acquired through microphones placed in close proximity to the test object) and acoustic noise sources within the turbofan duct are used for source reconstruction. This paper investigates the application of data smoothing techniques on source reconstruction in inverse boundary element method NAH. IBEM is chosen as the surfaces of turbomachinery are arbitrarily shaped. The measurement data is smoothed prior to inversion, and two separate smoothing (or denoising) techniques—exploratory data analysis and wavelet denoising—are compared for accuracy. Acoustic noise sources are subsequently estimated from the smoothed data using truncated singular value decomposition (TSVD) based regularized inversion techniques. [ABSTRACT FROM AUTHOR]

Abstract: In this work, the pressure fluctuation pattern in the volute of a squirrel-cage fan is analyzed. Also studied is how this pattern is modified when a slight geometry change is introduced in the volute tongue. The study has been carried out on a commercial machine, used in automotive air conditioning units. A three-dimensional and unsteady numerical simulation of the flow in the complete machine has been carried out using the commercial code FLUENT. In this way, the pressure fluctuations in some locations near the volute wall have been obtained. The results of this numerical simulation have been compared to the sound pressure level spectra radiated by the fan, measured in a ducted test installation at the laboratory. The tendencies of the sound pressure levels measured at the blade passing frequency show a good correlation with the amplitudes of pressure fluctuations obtained numerically near the volute wall. [Copyright &y& Elsevier]

This is the second of two companion papers that summarize the theoretical and experimental work carried out concerning modeling of dynamic properties of boring bars. This paper introduces the finite element method for the modeling of clamped boring bars. The "3-D" FE models of the system boring bar - clamping house as well as the "1-D" FE models of the clamped boring bar were derived. In particular, the modeling of the boring bar clamping is addressed. Dynamic properties predicted based on the developed FE models of the clamped boring bar were compared with the ones estimated by means of experimental modal analysis conducted on the actual boring bar clamped in the lathe. The "3-D" FE models display substantially higher correlation with the experimental modal analysis results compared to the "1-D" FE models. A "3-D" FE model of the boring bar - clamping house manages to model the distance in frequency and the orientation of the two fundamental modes to a large extent. The importance of the modeling of the boring bar boundary conditions for the accuracy of dynamic models of boring bars is demonstrated. The sensitivity of the natural frequency estimates produced by means of the FE and the continuous system (presented in Part 1) boring bar models with respect to variations in material density and Young's elastic modulus has been addressed. [ABSTRACT FROM AUTHOR]

Boring bar vibration is a common problem during internal turning operations and is a major problem for the manufacturing industry. High levels of boring bar vibration generally occur at frequencies related to the first two fundamental bending modes of a boring bar. This is the first of two companion papers that summarize the theoretical and experimental work carried out concerning modeling of dynamic properties of boring bars. This paper introduces the Timoshenko beam theory for the modeling of clamped boring bars. Also, the traditional Euler-Bernoulli beam theory is applied. These continuous system methods have been utilized to produce fixed-free beam models of the clamped boring bar. In order to improve accuracy of dynamic models of clamped boring bars, the modeling of the boring bar clamping is addressed by means of multi-span beam models with pinned boundary conditions. The derived boring bar models have also been compared with results obtained by means of experimental modal analysis, conducted on the actual boring bar clamped in a lathe. The multi-span beam boring bar models display higher correlation with experimental modal analysis results as compared to fixed-free beam models. For the fixed-free beams the Timoshenko model results in the highest correlation with the experimental results. On the other hand, the interval in frequency and the orientation of the two fundamental modes demonstrate differences, particularly between the continuous system models and the experimental results. [ABSTRACT FROM AUTHOR]

In operating the air-cleaner for a long time, people in a quiet enclosed space expect low sound at low operational levels for a routine cleaning of air However; in the condition of high operational levels of the cleaner; a powerful yet nonannoying sound is desired, which is connected to a feeling of an immediate cleaning of pollutants. In this context, it is important to evaluate and design the air-cleaner noise to satisfy such contradictory expectations from the customers. In this study, a model for evaluating the sound quality of air-cleaners of mechanical type was developed based on objective and subjective analyses. Sound signals from various air-cleaners were recorded and they were edited by increasing or decreasing the loudness at three wide specific-loudness bands: 20-400 Hz (0-3.8 barks), 400-1250 Hz (3.8-10 barks), and 1.25-12.5 kHz bands (10-22.8 barks). Subjective tests using the edited sounds were conducted by the semantic differential method (SDM) and the method of successive intervals (MSI). SDM tests for seven adjective pairs were conducted to find the relation between subjective feeling and frequency bands. Two major feelings, performance and annoyance, were factored out from the principal component analysis. We found that the performance feeling was related to both low and high frequency bands, whereas the annoyance feeling was related to high frequency bands. MSI tests using the seven scales were conducted to derive the sound quality index to express the severity of each perceptive descriptor Annoyance and performance indices of air-cleaners were modeled from the subjective responses of the juries and the measured sound quality metrics: loudness, sharpness, roughness, and fluctuation strength. The multiple regression method was employed to generate sound quality evaluation models. Using the developed indices, sound quality of the measured data was evaluated and compared with the subjective data. The difference between predicted and tested scores was less than 0.5 points. [ABSTRACT FROM AUTHOR]

Pressure pulsations in the piping system of the reciprocating compressor produce excessive noise and even lead to damage in piping and machinery. Therefore, it is very important to predict precisely the pressure pulsation with large amplitude in the piping system. In this paper, the finite disturbance theory is used to solve the nonlinear partial differential equations that describe the unsteady one-dimensional compressible flow in the complex piping system. The solution is then compared with experimental results. The comparison shows that the finite theory fits the large pressure disturbance more precisely than the acoustic theory. [ABSTRACT FROM AUTHOR]

The article summarizes the results of several studies on the effects of noise and vibration on machines and structures published in other periodicals. Short-interval period (SIP) distribution was found effective as fast Fourier transform (FFT) spectrum in the estimation of frequency response of a structure. Pews especially upholstered kneelers were found to provide sound absorption in churches. Blade loss simulation based on thermal growth effects was proposed for predicting ball contact load and stress in dual-rotor gas turbine engine.

The article describes how a six-person team at Siemens Power Generation in Erlangen, Germany turned powerful sounds into a whisper with the use of a computer simulated program. It states that a colour coded sound contour map is created and parameters are done to create a noise free neighborhood. Also discussed is the project launched by Professor Holger Hanselka of Germany's Fraunhofer Institute for Structural Durability (LBF) wherein new materials are created to make machines work quietly.

The article describes the limitations in applying the dB(A) criterion to oil and gas platform topsides. Particular focus is given on accommodation. It proposes a technique of applying the criterion to a scenario where there are high levels of low frequency noise and are therefore difficult to control. A description of the acoustic environment on oil 8 gas platforms is presented. Also detailed are ways how the sound is attenuated.

Abstract: A sensor for froth acoustic emission detection, capable of isolating the external noise produced by machinery in the concentrator, has been recently developed and tested. The froth acoustic emission technique involves the use of ultrasonic sensors to measure the elastic energy released by film rupture during bubble coalescence in industrial flotation cells. The signal emitted by the sensor has been proven to respond to changes in froth conditions. This signal, the acoustic emission activity of the froth phase, provides an alternative method to measure the stability of the froth. This device has been recently tested in industrial size flotation cells, measurements were performed in different cells along a flotation bank where differences in the froth phase between cells can be appreciated in steady state. The sensor has also been tested in a pilot cell (3m3), operating with different frothers and concentrations. The response of the sensor to changes in metallurgical performance are shown in this paper and compared with other instrumentation outputs. [Copyright &y& Elsevier]

This paper considers the noise generated by interaction between the rotor blade and the exhaust grille. Acoustic measurements were first performed in a semianechoic chamber to investigate the characteristic of the noise. An approach that combines a Reynolds averaged Navier-Stokes calculation with the stochastic noise generation and radiation method is used to identify noise sources. With the computed flow solutions, the broadband noise radiated by the grille is evaluated based on a semi-empirical noise model. The numerical results are compared with the measured noise levels and good agreement is obtained. [ABSTRACT FROM AUTHOR]

Abstract: Vibration-based analysis is an important technique in machine fault diagnosis. In complex machines, the vibration generated by a component is easily affected by the vibration of other components or is corrupted by noise from other sources. Hence, the fault-related vibration must be recovered from among those sources for accurate diagnosis. In this paper, a super-exponential algorithm (SEA) based on the single-input single-output (SISO) convolution mixing model is investigated to deconvolve the vibration signal of interest. Based on simulated vibration signals generated by a test bench in a laboratory and real signals generated by industrial machines, the characteristics of the SEA with skewness and kurtosis schemes are studied extensively for the recovery of signals with different statistical distributions. It is shown that the SEA with the skewness scheme is more suitable for the isolation of a vibration signal with an asymmetric distribution, whereas the SEA with the kurtosis scheme is more efficient for detecting a vibration with abrupt changes in its distribution. Furthermore, the effect of the equalizer length on the characteristics of the equalized signal is discussed. A performance curve that presents the equalization performance is defined, and a method that uses this curve to select the optimal equalizer length for successfully recovering the defect signal from the mixed signal is then proposed. The study presented in this paper thus shows that the SEA is a promising method for the recovery of vibrations in machine fault diagnosis. [Copyright &y& Elsevier]

Abstract: Ball end milling is one of the most widely used cutting processes in the automotive, aerospace, die/mold, and machine parts industries, and the chatter generated under unsuitable cutting conditions is an extremely serious problem as it causes excessive tool wear, noise, tool breakage, and deterioration of the surface quality. Due to the critical nature of detecting and preventing chatter, we propose a dynamic cutting force model for ball end milling that can precisely predict the cutting force for both stable and unstable cutting states because our uncut chip thickness model considers the back-side cutting effect in unstable cutting states. Furthermore, the dynamic cutting force model considers both tool runout and the penetration effect to improve the accuracy of its predictions. We developed software for calculating the cutting configuration and predicting the dynamic cutting force in general NC machining as well as single-path cutting. The chatter in ball end milling can be detected from the calculated cutting forces and their frequency spectra. A comparison of the predicted and measured cutting forces demonstrated that the proposed method provides accurate results. [Copyright &y& Elsevier]

Abstract: Fretting wear damage is frequently reported in the races of rolling element bearings and leads to the increased noise and vibration in the total machinery. The fretting wear studies were conducted on the as-received and hardened and tempered En 24 steel fretted against hardened and tempered bearing steel, En 31. Tests were conducted at different normal loads under unlubricated dry conditions. The coefficient of friction depends on the contact conditions, whether it is gross slip or stick slip. Hardness has only marginal effect on improving the fretting wear resistance. [Copyright &y& Elsevier]

Abstract: Structure-borne noise generated by marine vessels is an area that receives much research attention. Significant noise levels are generated due to onboard machinery such as the diesel engines, gearboxes, generators, and auxiliary machinery. In the case of ships and submarines, a major source of the radiated noise at low frequencies is due to excitation of the hull modes resulting from vibration transmission through the propeller-shafting system. Oscillations occur at the propeller due to small variations in thrust when the propeller blades rotate through the non-uniform wake, resulting in axial excitation of the propeller at the blade pass frequency. This problem can be addressed by the use of a resonance changer (RC) which performs the task of a hydraulic dynamic vibration absorber, thereby reducing the vibration transmission and avoiding excitation of hull axial resonances. This research is concerned with optimisation of both single and dual RC configurations in a submarine. An optimisation scheme involving a genetic and a general nonlinear constrained algorithm is used to minimise two fitness functions associated with the vibration transmission to the hull over a low-frequency range. The dynamic response of the propeller-shafting system is characterised using the transmission matrix approach. This modular description enables greater flexibility for dynamic modelling of the propeller-shafting system, and can be easily manipulated for future design modifications. [Copyright &y& Elsevier]

High quality manufactured products are expected to behave essentially identically. However, the measurement of a frequency response function on nominally identical products will typically show significant variation in the dynamic behavior. The dynamic behavior of manufactured products in the frequency range of interest for most noise control applications as measured by frequency response functions are highly sensitive to uncontrolled aspects of manufacturing processes and uncontrolled aspects of the experiment. In this paper, data from well controlled experiments on nominally identical pickup trucks, diesel engines and compressor housings are reported in order to illustrate the variation found in typical manufactured products. The variation in the frequency response functions is also examined in order to identify statistical properties that can be expected of manufactured products. Post-processing of the coefficient of variation for this data is studied as a metric to characterize these product variations. [ABSTRACT FROM AUTHOR]

The measurement of noise emission from machinery, of which measurement uncertainty is a crucial aspect, has been an issue for regional and international standardization for many years. In Europe, the interest in noise emission has resulted mostly from European regulations. These regulations have required manufacturers to design machines and equipment with the lowest possible noise emission and to provide customers with noise emission data when putting new items on the European market. In addition, regulations recommend users to purchase low noise emission machines. A variety of accompanying technical documents have been drafted in order to assist experts in drafting standardized noise test codes. These are key standards in that they provide detailed specifications for the measurement and the declaration of noise emission values and, by doing so, they must deal with measurement uncertainty. Data obtained from these standards allow manufacturers to assess noise reduction achieved at the design stage and users to compare noise emissions of machines on the market and to assess effects on noise exposure. An overview of the treatment of uncertainty in standards on noise emission from machinery is presented. [ABSTRACT FROM AUTHOR]

Abstract: The mathematical models representing machine tool chatter dynamics have been cast as differential equations with delay. In this paper, non-linear delay differential equations with periodic delays which model the machine tool chatter with continuously modulated spindle speed are studied. The explicit time-dependent delay terms, due to spindle speed modulation, are replaced by state-dependent delay terms by augmenting the original equations. The augmented system of equations is autonomous and has two pairs of pure imaginary eigenvalues without resonance. The reduced bifurcation equation is obtained by making use of Lyapunov–Schmidt Reduction method. By using the reduced bifurcation equations, the periodic solutions are determined to analyze the tool motion. Analytical results show both modest increase of stability and existence of periodic solutions near the new stability boundary. [Copyright &y& Elsevier]

A hypersingular boundary integral method for the prediction of radiation from a straight circular pipe with arbitrary end profile has been developed. The technique represents an extension of established procedures for axisymmetric pipes with the addition of recent advances in special function and quadrature theory to simplify the implementation. The resulting code is applied to two sample problems: first, the prediction of radiation of a plane wave mode from a pipe with its ends cut by an inclined plane, representing the “scarfed intake” proposed for reduction of aircraft engine noise. Second, the method is used to examine scattering of an incident azimuthal mode by a multi-lobed profile, characteristic of the “chevron” nozzles proposed for jet engine exhausts. [ABSTRACT FROM AUTHOR]

Abstract: Agricultural mechanization in Japan has progressed dramatically since 1955 with the introduction of tractors, harvesters, and processing machines. These technological developments have resulted in an increase in exposure to sources of noise that are not only annoying, but damaging to hearing. The present study was undertaken to determine, whether Japanese farmers are at risk for noise-induced hearing loss in comparison with office workers, and by evaluating the present conditions regarding occupational noise levels among agricultural workers. The results suggest that farmers, especially male farmers, have a high prevalence of hearing loss in the higher frequency ranges. Daily noise exposure levels in ranged from 81.5 to 99.1dBA for tea harvesting and processing, and from 83.2 to 97.6 for sugar cane harvesting. Taking into account their rather long working hours and excessive noise from farm machinery, it is concluded that farmers are at risk for noise-induced hearing loss. These findings clearly indicate a strong need for implementation of hearing conservation programs among agricultural workers exposed to machinery noise. [Copyright &y& Elsevier]

The section of "Comfort Properties of Textiles," deals with the problem of noise in the textile industry. It is stated that the emission of noise during textile processing is a notorious feature of the industry. A researcher has given a general discussion of the factors that govern the generation of noise by machinery, along with a summary of methods suggested for its absorption and reduction. Another researcher points out that noise control is a burden that must be shouldered by the industry as a whole. Several authors have worked on measurements of the noise levels to which employees are exposed in a working environment. The most tangible effect of noise exposure is the loss of hearing. In many countries, legislation to control high sound levels is in force or under consideration.

The article explores solutions to engine-room noise problem on board merchant ships. The deleterious effects that noise from machinery and equipment might have on the health of seafarers was addressed by the 19th Session of the Joint Maritime Commission of the International Labour Office. It provides a historical background of the study of noise. The two primary measurements of noise are the frequency, or the number of successive pressure waves per second and the maximum pressure or force of these waves. It discusses the harmful effects of noise on man.

The noise levels in Dundee weaving sheds, as in other mills in which traditional looms are in operation, constitute an appreciable hazard to hearing when weavers are exposed over a period of from ten to fifteen years to noise levels in the range 99-101 dB. This paper describes an attempt to reduce loom noise by the substitution of plastics materials for metallic bearing and impact surfaces. The noise reduction achieved in a test loom by substituting plastics components was found to be of the order of only 2-3 dB, limited to the range 0·5-2·0 kc/s. Although small reductions of this order are desirable and worth while, loom-noise levels at present are far above the Damage Risk Criteria for human hearing, and efforts on the part of loom manufacturers to reduce over-all noise levels will require to be made, especially in new machinery. [ABSTRACT FROM AUTHOR]

The current situation of vibration and noise reduction of needle loom as well as damping technology were summarized in this article. Based on analyzing the source of vibration and noise, the existing problems and development trends of needle loom, the authors introduced the application of damping technology. Besides, some countermeasures for reducing the vibration and noise of needle loom were also put forward. [ABSTRACT FROM AUTHOR]

The article presents summaries of several studies on the effects of noise and vibration on machines and structures published in various periodicals. One study proposed a stochastic method for damage detection and identification in the shafts of rotating machines. An experimental study examines the noise reduction of an industrial forward-curved (FC) blades centrifugal fan. Another research focuses on the vibration of suspended bridges subjected to moving loads and vertical support motions due to earthquake.