How to solve the problem of noise exposure evaluation under complex conditions in the field

1 objects and methods

The research object is two groups of workers who operate and manage low-pressure air compressors and high-pressure air compressors in a factory. Among them, 3 low-pressure air compressors and 5 high-pressure air compressors are used as measurement targets for noise exposure. Since the measurement is only started in the morning in the summer, the individual meter is used to measure the 4-hour noise exposure data, and the tested workers are recorded at the same time.

The individual noise exposure data of each worker was measured with a domestic SH126 recording sound level meter. The instrument is carried around and is fixed every 02 seconds! 203! China Industrial Medicine Journal, Vol. 13 No. 4, 2000, collects noise data in a microphone near the ear, and puts the result into memory, recording a set of data every 10 minutes for 4 hours. The collected data is input into the IBM microcomputer through the RS232 serial port and stored in the microcomputer for further analysis.

Measurement data The SH126exe software was used to plot the histogram of the dynamic change of the noise exposure level during the work, and the 4-hour equivalent continuous A sound level (LAeq. 4h) was calculated. The average level of noise exposure and its standard deviation for each worker on different working days and the average level of noise exposure and the standard deviation of each group of workers during each working day were calculated separately. An analysis of variance was used to test for differences in noise exposure between working days and between workers to assess the internal consistency of noise exposure for each group of workers.

While using the individual meter to measure, the HS5670 sound level meter is used to measure the average continuous A sound level (LAeq.1min) of the typical worker's ear height in the workshop. The average value of the ambient noise of each workshop is calculated. And standard deviation.

2 results

The dynamic variation of the typical four-hour individual noise exposure of the low-pressure and high-pressure air compressor operators shows that the noise exposure level fluctuates during the working period, and the fluctuation range can reach about 10dB(A). By reviewing the working hours record, the cause of fluctuations in the noise exposure level is related to the working state of the machine (starting or stopping), the worker's working position, and the like. Different workers have different consistency in individual noise exposure patterns on different working days.

The average individual noise exposure level of low-pressure air compressor operators was 858dB(A). There was no significant difference in noise exposure between workers and working days after variance analysis (P>005), suggesting that the noise exposure of this group of workers has Internal homogeneity, similar to noise exposures between different workdays, is consistent with a working assumption that assumes similar noise exposure for this group of workers. The individual noise exposure of the high pressure air compressor operator has an average exposure level of 857 dB(A).

The results of multi-point measurement by the ordinary sound level meter in the work of these two workshop workers are: the average noise level of the working environment of the low-pressure air compressor operator (86127) dB(A), high-pressure air compressor (83827) dB(A) ).

3 Discussion

This paper observes the noise exposure of two groups of typical air compressors. Interestingly, the ambient noise level measured by the classical method is lower than 85dB(A) for high-pressure air compressors and 85dB(A) for low-pressure air compressors, while individual noise exposures measured by individual meters are higher than 85dB(A), there is a certain difference between the results of the two measurement methods. In recent years, the level of restrictions on the production environment noise exposure in the world has gradually become stricter, mostly tending to 85dB (A), and the Ministry of Health recently issued the Industrial Enterprise Staff Hearing Protection Specification # also 85dB (A) as the implementation of this regulation! 204! ChineseJIndMed, the starting point of Aug2000, Vol.13No.4. In the future implementation of the Hearing Protection Specification for Industrial Enterprise Employees, whether the actual level of worker's 8-hour exposure to noise exceeds 85 dB (A) will determine whether workers should be included in the hearing protection plan, and whether further measures should be taken to reduce workers' noise exposure. Therefore, accurate measurement and evaluation of workers' actual noise exposure levels is of great practical significance. Taking this article as an example, the individual noise exposure measurement and evaluation results of 857dB(A)% suggest that the high-pressure air compressor operator should be included in the hearing protection plan; the result of the workshop environmental noise measurement method is 838dB(A)%, which does not need to be taken further. Prevention.

It is known that the noise exposure of most production sites is very complicated, whether the noise generated by the noise source is stable, the relative position between the worker and the noise source is fixed, the relationship between multiple noise sources and workers, etc., using the classical fixed point. The method is difficult to evaluate the noise exposure of workers in complex situations. In contrast, the measurement of individual noise exposure becomes a means of better reflecting the actual noise exposure of workers. It can be seen from the results of Fig. 1 and Fig. 2 that the individual meter can record the fluctuation of the individual noise exposure level caused by the change of the working state of the machine and the movement of the worker's working position, which makes up for the deficiency of the classical method to measure the noise exposure.

With the development of electronic technology and the emergence of domestic noise individual meters, it has become achievable to measure the noise exposure of individuals. In the research process of this subject, we found that the SH126 recording sound level meter can initially meet the needs of the production site to measure the individual noise exposure of workers. Through continuous improvement, such instruments will be more and more adapted to the needs of on-site individual noise exposure measurement, and may be widely used in practical work of labor hygiene in the future.

To evaluate the noise exposure of a group of workers, it is necessary to consider whether there is a difference in the noise exposure between workers and the range of their variation. It is also necessary to consider the fluctuation of the noise exposure level and the range of variation caused by various conditions such as changes in production conditions on different working days. To this end, we designed a number of workers as a target for observation according to the principle of statistical null hypothesis (there are few people in each group, so all are selected), and observe individual noise exposures on different working days. The results confirm that the noise exposure variation we have envisaged does exist. If we do not pay attention to the variation of noise exposure between individuals and during the working day, it may cause a large error in the noise exposure evaluation. As shown in Table 1, the extreme values ​​of individual noise exposure measurements are 801dB(A) and 894dB(A), respectively, which is far from the average of 858dB(A). If one person uses one measurement, it is possible to use one measurement. The noise exposure levels of this group of workers were estimated too high or too low.

The measurement and evaluation of individual noise exposure is a new field. This paper discusses the related technical issues. At present, it has been able to measure and evaluate more objectively and accurately, but the workload is large, and it is difficult to avoid the need for many individual meters to work at the same time. In the future research and practical work, it is necessary to further consider how to improve this technology, make it simple and easy, and gradually standardize and standardize.

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