نتایج جستجو برای: high frequency noise

تعداد نتایج: 2520513  

ژورنال: تحقیقات موتور 2018
Asadi, M., Baloo, M., Jafari, M. J.,

Valvetrain is one of the major sources of noise and vibration in IC engines. The importance of cam surface quality parameters is highlighted in the valve train mechanisms with direct sliding contact between cam and tappet. In this paper, the influence of surface quality parameters on high frequency noise producing is investigated. The roughness and waviness of some intake and exhaust camshafts ...

Journal: :journal of electrical and computer engineering innovations 2014
sattar samadigorji bijan zakeri mohammadreza zahabi

the aim of this paper is to minimize output phase noise for the pure signal synthesis in the frequency synthesizers. for this purpose, first, an exact mathematical model of phase locked loop (pll) based frequency synthesizer is described and analyzed. then, an exact closed-form formula in terms of synthesizer bandwidth and total output phase noise is extracted. based on this formula, the phase ...

ژورنال: سلامت کار ایران 2017

Background and aims Nominal noise reduction rating of the earmuff manufacturers can be different compared with the actual noise attenuation rating. The current study aimed to determine the actual noise reduction rate of current hearing protection devices in the real workplaces using a field microphone in real ear method (FMIRE). Methods: In this cross-sectional study, five common earmuffs we...

Introduction: Hearing loss is one of the most common occupational diseases. In most workplaces, workers are exposed to noise and solvents simultaneously, so the potential risk of hearing loss due to solvents may be attributed to noise.  In this study we aimed to assess the effect of exposure to mixed aromatic solvents on hearing in the absence of exposure to hazardous noise.   Materials and Met...

Journal: :iranian journal of medical physics 0
bahareh shalchian ph.d. student, medical physics dept., faculty of medical sciences, tarbiat modares university, tehran, iran hossein rajabi associate professor, medical physics dept., faculty of medical sciences, tarbiat modares university, tehran, iran hamid soltanian-zadeh professor, control and intelligent processing center of excellence, electrical and computer engineering dept., university of tehran, tehran, iran

introduction: an efficient method of tomographic imaging in nuclear medicine is positron emission tomography (pet). compared to spect, pet has the advantages of higher levels of sensitivity, spatial resolution and more accurate quantification. however, high noise levels in the image limit its diagnostic utility. noise removal in nuclear medicine is traditionally based on fourier decomposition o...

Journal: :journal of health sciences and surveillance system 0
masoud neghab department of occupational health engineering, school of health, and research center for health sciences, shiraz university of medical sciences, shiraz, iran; hamid karimi student’s research committee, department of occupational health engineering, school of health, shiraz university of medical sciences, shiraz, iran; sayed hamidreza tabatabaee department of epidemiology, school of health, shiraz university of medical sciences, shiraz, iran esmaeel soleimani student’s research committee, department of occupational health engineering, school of health, shiraz university of medical sciences, shiraz, iran; abas ali kasaeinasab student’s research committee, department of occupational health engineering, school of health, shiraz university of medical sciences, shiraz, iran;

background: noise is one of the most pervasive hazards in industrial settings. this retrospective study was carried out to assess the effects of noise exposure on hearing status, blood lipids and blood pressure of employees of a local fireclay mine. methods: two hundred and forty male workers were studied. data on audiometric measurements, blood lipids and blood pressure were derived from the w...

Journal: :journal of research in health sciences 0
rostam golmohammadi mohammad reza monazzam maryam nourollahi ali nezafat samaneh momen bellah fard

background: the adverse effects of noise are well known and noise problems due to industrialization of communities are increasing over the time. oil industries due to the process and nature of production; contain many noise sources such as compressors, turbines, and pumps, which cause excessive noise exposure. the objective of this study was to evaluate the noise characteristics of compressors ...

ژورنال: فیزیک زمین و فضا 2018

Time-frequency filtering is an acceptable technique for attenuating noise in 2-D (time-space) and 3-D (time-space-space) reflection seismic data. The common approach for this purpose is transforming each seismic signal from 1-D time domain to a 2-D time-frequency domain and then denoising the signal by a designed filter and finally transforming back the filtered signal to original time domain. ...

Background and Objectives: Noise pollution in cities, as a widespread and worldwide problem, can cause adverse health effects such as hearing loss. Traffic noise, as the most important source of urban noise, can influence many jobsincluding shopkeepers. The aim of this study was simultaneous assessment of traffic noise pollution and hearing threshold level of shopkeepers in congested area of Be...

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