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This paper aims to investigate the friction noise properties of M50 matrix curved microporous channel composites filled with solid lubricant Sn-Ag-Cu (MS).

Pure M50 (MA) and MS are prepared by selective laser melting and vacuum-pressure infiltration technology. The tribological and friction noise properties of MA and MS are tested through dry sliding friction and then the influential mechanism of surface wear sate on friction noise is investigated by analyzing the variation law of noise signals and the worn surface characteristics of MS.

Experimental results show that the friction noise sound pressure level of MS is only 75.6 dB, and it mainly consists of low-frequency noise. The Sn-Ag-Cu improves the surface wear state, which reduces self-excited vibration of the interface caused by fluctuation of friction force, leading to the decrease of friction noise.

This investigation is meaningful to improve the tribological property and suppress the friction noise of M50 bearing steel.

This paper deals with the investigations carried out on the variation of current noise (1/f noise) in polymer thick film resistors, when they are subjected to pulse voltage trimming. The current noise is measured in terms of noise index (micro volts of noise per volt of DC applied, in a decade of frequency) using Noise Meter Model 315 C manufactured by Quan‐Tech of New Jersey. It has been found that current noise decreases as the resistors are trimmed to lower values. An attempt has been made to explain the decrease in current noise with the trimming of resistors.

Suggests that before measurement of noise can be implemented all “non‐aircraft noises” must be eliminated. Sets out various approaches to the problem of airport noise: the acoustic companies’ approach; the systems companies’ approach; systems costs; flight identification and correlation; and noise monitoring. Looks at international standards for noise monitoring and reports on the current noise monitoring terminal situation. Includes an Appendix on units of measure for noise.

This article is a proposal and aims to be a first step to develop a method to evaluate and classify environmental noise, according to EN‐15251 and CR‐1752, in the built environment based on the percentage of dissatisfied related to the equivalent background noise level.

In the European guideline CR‐1752 and the standard EN‐15251 three categories of the indoor environment in buildings are prescribed (category A, B and C). In the recommendations, the limit whereby the percentage of dissatisfied should remain under varies in each category for both the thermal indoor environment and the air quality. The categories for noise and illumination criteria are not yet explicitly related to a percentage of dissatisfied.

Using the percentage of dissatisfied as the evaluation criterion, when related to the equivalent background noise, produces a more refined evaluation of comfort than an evaluation based on the percentage of seriously disturbed or the effects of sleep deprivation in relation to external noise. Furthermore, this corresponds to the European standards and recommendations concerning quality classification of the indoor environment, based on the percentage of dissatisfied.

Based on recent European undertakings concerning the development of categories for the indoor environment based on the percentage of dissatisfied, it is desirable to utilise these categories to noise aspects too, and to relate it to the equivalent background noise level.

DURING the 1950s noise around airports increased steadily with increasing traffic and size of aircraft. With the introduction of heavy jet transports the very different quality of noise (compared to piston engines) highlighted the problem and the upward trend had to be halted. This led to a considerable increase in effort to investigate the noise of turbojet engines.

A concept and an implementation of the multimedia computer system for the monitoring of environmental noise is presented in the paper. The system provides an extension to the Internet‐based system for testing hearing which was engineered and launched in 1999. A considerable portion of hearing diseases is caused by excessive industry, urban and traffic noise or any unwanted sounds occurring in everyday life. Consequently, it is expected that a reduction of hearing diseases occurrence will be achieved as a result of implementation of the solutions that have been developed within the project scope. The latest technological advances in information technology were used in the course of the project realisation. Consequently, it is shown in the paper that the presented solutions are based on some innovative ideas and inexpensive technical means for measuring noise and vibration allowing fast evaluation of its influence on the psychosomatic and the vegetative system. It is expected that implementation of the noise telemonitoring system covering whole country will contribute to rising awareness of society and authorities with regard of the influence of noise on health. Furthermore, it turns out to be an essential factor in the future improvement of the environmental noise conditions.

This study aims to investigate the noise-inducing characteristics during the start-up process of a mixed-flow pump and the impact of different start-up schemes on pump noise.

This study conducted numerical simulations on the mixed-flow pump under different start-up schemes and investigated the flow characteristics and noise distribution under these schemes.

The results reveal that the dipole noise is mainly caused by pressure fluctuations, while the quadrupole noise is mainly generated by the generation, development and breakdown of vortices. Additionally, the noise evolution characteristics during the start-up process of the mixed-flow pump can be divided into the initial stage, stable growth stage, impulse stage and stable operation stage.

The findings of this study can provide a theoretical basis for the selection of start-up schemes for mixed-flow pumps, reducing flow noise and improving the operational stability of mixed-flow pumps.

Examines the problem of noise level of civil aircraft engines. Focuses on two aspects of aircraft fan noise: cabin noise and community noise. Outlines the FANPAC programme launched in 1992 to assess techniques to control fan noise and describes two of the most promising liner designs. Reports on the progress made and suggests a follow‐on programme to explore further areas.

The purpose of this paper is to analyze the effect of the white, colored and mixture noise perturbations as Gaussian process on the parameters of the RL electrical circuit including potential source and resistance.

By adding different noise terms in the voltage and resistance parameters of an RL electrical circuit, the deterministic model is replaced by a stochastic differential equation (SDE).

Owing to the application of multiple Ito's formula the analytical solutions of resulted SDEs have been obtained. Furthermore, based on a numerical method involving Euler‐Maruyama scheme, the solution of the problem at the point of interest as a continuous time stochastic process has been obtained. Also shown is that the confidence interval for mean of solutions with colored and mixture noises is better than white noise.

Numerical tests via Matlab programming are performed in order to show the efficiency and accuracy of the present work. Numerical experiments show that an excellent estimation on the solution can be obtained within a couple of minutes time at Pentium IV‐2.4 GHz PC.

It is believed that the stochastic model of an RL circuit with colored and mixture noises in potential source has not been studied before. Furthermore, according to latest information from the research works, two stochastic parameters in voltage and resistance of RL circuit including colored and mixture noise processes have been investigated for the first time in this paper.

The purpose of this paper is to detect edge of image in high noise level, suffering Gaussian noise.

Canny edge detection algorithm performs poorly when applied to highly distorted images suffering from Gaussian noise. In Canny algorithm, 2D‐gaussian function is used to remove noise and preserve edge. In high noise level, 2D‐gaussian function cannot meet the needs. In this paper, an improving Canny edge detection algorithm is presented. The algorithm presented is based on local linear kernel smoothing, in which local neighborhoods are adapted to the local smoothness of the surface measured by the observed data. The procedure can therefore remove noise correctly in continuity regions of the surface, and preserve discontinuities at the same time.

The statistical model of removing noise and preserving edge can meet the need of edge detection in images highly corrupted by Gaussian noise.

It was found that when the noise ratio is higher than 40 percent, the edge detection algorithm performs poorly.

A very useful method for detecting highly distorted images suffering Gaussian noise.

Since an image can be regarded as a surface of the image intensity function and such a surface has discontinuities at the outlines of objects, this algorithm can be applied directly to detect edge of image in high noise level.