Work environment affects human productivity and his performance. The aims of this study were to investigate the effects of lighting and noise levels on human productivity in the automotive assembly industry. Method. Subjects were 181 workers from different parts of an automobile assembly industry. Illuminance (Lx) at the height of 30 inches from the surface of work station and noise (dBA) were locally measured. Also human productivity by the Goldsmith and Hersey scale (1980) was measured. Data were analyzed by using SPSS v20 Pearson correlation coefficient. Results. The results showed that the relationship between noise level and human productivity is negative and significant (P < 0.05, r = −0.178), but there was no significant relationship between lighting and human productivity (P > 0.05). Conclusion. Based on the results, in assembly tasks, noise has a negative impact on human productivity, and lighting does not affect this. So, in order to increase employee productivity, noise control and reduction to less than the standard values (less than 85 dB) is necessary.

Background:Analyzing the possible negative effects of using cell phones on the users’ health is an important and vital affair due to rapid growth and extensive use of these devices on human communications and interactions. The aim of this study was to determine the effect of increasing the distance of cell phones to brain tissue on the temperature of the central and gray matters of brain due to the heat generated by radio frequency waves.Methods:This study was an experimental study. A cow's brain tissue was analyzed in a compartment with three thicknesses of 2, 12, and 22 mm, in the distances of 4 mm and 4 cm from a cell phone for 15 min. Lutron thermometer was used to measure the tissue temperature, and the data analysis were done by Lutron and MATLAB software packages.Results:The tissue temperature was increased while confronting with a cell phone in distances of 4 mm and 4 cm in all the three thicknesses of 2, 12, and 22 mm. The tissue temperature was higher after removing the confrontation at 4 mm distance as compared to the distance of 4 cm.Conclusions:During confrontation and after that with the cell phone, reducing the distance of brain tissue and the cell phone increased the tissue temperature intensely. In fact, by increasing the cell phone distance from brain tissue, the thermal effect of radiofrequency waves was reduced.

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Sound is one of the most important problems in industrial environments, and it causes hearing loss at different frequencies in the workforce. Incorrect fitting of hearing protector has a negative effect on noise reduction. The present study was conducted with the aim of determination of the effective frequencies on hearing loss and variations of the sound level in different frequencies after placing the earplug. A model of ear canal with different materials was simulated. Sound pressure sensors and earplugs were placed in both sides of the ear canal. The rates of sound reduction in octave frequency signals were calculated for the simulated canal of different materials, in different distances between the microphone and the earplug with Labview software. The results of sound simulation in octave frequency signals showed that by increasing the frequency, the rates of sound reduction in different conditions also had an increasing trend. The obtained peak rates for all the situations coincided with each other at fixed frequencies. In most cases, a noise reduction in the frequency of 4000 Hz showed a high number. The maximum sound reduction was observed at 25.5 mm at frequencies below 250 Hz, which was similar to the average of human ear canal length; so the simulated model can be used to determine the performance of the protective earphones and test them at different frequencies and sound pressure levels.

Different ways are used in our ears to the best possible impedance matching achieved, and somehow the impedance mismatch that is released. These ways are the greater area of the eardrum to the oval window, and amplification actions of the middle ear ossicle, the ear canal, shoulder, head, and pinna. →What this article adds:Based on our knowledge, these amplification mechanisms have been neglected in the occupational health-related noise measurements and the hearing protection programs; thus, in this study, the effects of the external auditory canal on the total sound pressure level and sound pressure levels at different frequencies were studied. Also, 3 SSPLs that are usual in the workplaces were used in this research. The ear canal can amplify the sounds and increase the sound pressure levels. This amplification is found to be greater in men than in women. The resonance ability of the ear canal is larger in some frequencies, especially in higher frequencies. This ability of the ear canal should be considered in the workplace noise evaluations.

Noise may be defined as any unwanted sound. Sound becomes noise when it is too loud, unexpected, uncontrolled, happens at the wrong time, contains unwanted pure tones or unpleasant. In addition to being annoying, loud noise can cause hearing loss, and, depending on other factors, can affect stress level, sleep patterns and heart rate. The primary object for determining subjective estimations of loudness is to present sounds to a sample of listeners under controlled conditions. In heating, ventilation and air conditioning (HVAC) systems only the ventilation fan industry (e.g., bathroom exhaust and sidewall propeller fans) uses loudness ratings. In order to find satisfaction, percent of exposure to noise is the valuable issue for the personnel who are working in these areas. The room criterion (RC) method has been defined by ANSI standard S12.2, which is based on measured levels of in HVAC systems noise in spaces and is used primarily as a diagnostic tool. The RC method consists of a family of criteria curves and a rating procedure. RC measures background noise in the building over the frequency range of 16-4000 Hz. This rating system requires determination of the mid-frequency average level and determining the perceived balance between high-frequency (HF) sound and low-frequency (LF) sound. The arithmetic average of the sound levels in the 500, 1000 and 2000 Hz octave bands is 44.6 dB; therefore, the RC 45 curve is selected as the reference for spectrum quality evaluation. The spectral deviation factors in the LF, medium-frequency sound and HF regions are 2.9, 7.5 and -2.3, respectively, giving a Quality Assessment Index (QAI) of 9.8. This concludes the QAI is useful in estimating an occupant's probable reaction when the system design does not produce optimum sound quality. Thus, a QAI between 5 and 10 dB represents a marginal situation in which acceptance by an occupant is questionable. However, when sound pressure levels in the 16 or 31.5 Hz octave bands exceed 65 dB, vibration in lightweight office construction is possible.

This paper focuses on measurement and prediction of hand-arm vibration generated when a rock drill is used in stone mines using a B & K vibration meter 2512. In order to evaluate them, we had to locate the hand-arm acceleration levels on the handles of pneumatic hammers while the operator was standing and processing his work. The method of "Pneurop Cagi Test Code" is designed to evaluate noise and vibration propagated by hand-held pneumatic tools. The evaluation of Hand-Arm vibration in hand -held pneumatic tools (Rock drills) used in the lashotor stone mines in Isfahan by the method of the "Pneurop Cagi Test Code" shows methods which are provided to use construction equipment in stone mines under work circumstances. The paper demonstrates measured vibration level values in three directions X, Y, Z for workers while working with equipment, compared to standard values, and a produced by a "Rock Drill" used in the above specifies test method, but reported in only two directions, y and z due to vibration being very low at the x-direction. The found conclusions have shown high values of rms acceleration especially in the Z direction for a wide range of exposure frequencies based on BS EN ISO 5349-1, 2: 2002 standards.

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