Study on the effect of noise on the hearing of the SU-30 aircraft maintenance soldiers

SU-30 aircraft is a modern fighting aircraft in Vietnam. The noise of the aircraft’s engine with high frequency and intensity will have effect on the hearing of the soldiers, specially aircraft maintenance soldiers. This study was carried out to investigate the noise levels in some working areas and the effect of noise on the hearing of the Su-30 aircraft maintenance soldiers.

STUDY ON THE EFFECT OF NOISE ON THE HEARING OF THE SU-30 AIRCRAFT

MAINTENAnCE SOlDIERS

Nguyen Minh Phuong*; Nguyen Van Chuyen*

Nguyen Van Ba: Nguyen Tung Linh*

SUMMARY

SU-30 aircraft is a modern fighting aircraft in Vietnam The noise of the aircraft’s engine with high frequency and intensity will have effect on the hearing of the soldiers, specially aircraft maintenance soldiers This study was carried out to investigate the noise levels in some working areas and the effect of noise on the hearing of the Su-30 aircraft maintenance soldiers The results showed that the sound intensity levels in working areas of Su-30 aircraft maintenance soldiers in the airport as well as maintenance area were higher than hygienic standards The highest sound intensity level was 120 dB The rate of hearing loss among SU -30 aircraft maintenance soldiers was quite high (23.9%) The higher seniority, the higher rate of hearing loss and their higher level of hearing loss in SU-30 aircraft maintenance soldiers

* Key words: Noise; Hearing; Aircraft maintenance soldiers

Introduction

Noise is one of the factors that cause working environmental pollution According to accountance of the World againts noise association, there were from 1/4 to 1/3 workers have to work in working environment with high sound intensity level that can impact on the hearing of workers

In the military working condition, there are many arms in which soldiers have to work in environment with high sound intensity level such as artillery, tank, airforce, navy, corps…

In Air Force, the noise caused by aircraft engine with high frequency and intensity which can be harmful to the health of soldiers, specially aircraft maintenance soldiers who have to be exposed to the noise directly

SU-30 aircraft is a modern fighting aircraft in Vietnam The investigation of the noise caused

by SU-30 aircraft as well as the effect of noise on the hearing of aircraft maintenance soldiers is

very necessary Therefore, we have carried out this study in order to: Investigate the noise levels in some working areas and the effect of noise on the hearing of the SU-30 aircraft maintenance soldiers

Subjects and methods

1 Subjects

- Measurements the sound intensity levels in some working areas of Su-30 aircraft maintenance soldiers in airport and technical maintenance area of air-base X, Vietnam Air Force

Some places were measured sound intensity level as followed:

+ Refueling and technical checking places during preparation for taking off and landing

+ Technical maintenance area: Technical room, maintenance place and outside

- 88 soldiers who are working as SU-30 aircraft maintenance staff in air-base X, Vietnam Air Force

2 Methods

* Measuring method of sound intensity level:

The sound intensity levels were measured using noise measurement range machine (RION NL-04, Japan) The micro of this machine was kept as high as the ear and measured from the 0.5

m Measurement was carried out at least 3 times in each place and the average number was recorded Unit of the sound intensity level is dBA

* Measuring method of hearing:

- Measuring instruments:

+ Sound insulation room: Using a small room which has maximum background sound of 35

dB

+ Measurement of hearing machine: Measurement of hearing was carried out using Phillip A70 machine which has 7 frequencies: 125; 250; 500; 1,000; 2,000; 4,000 and 8,000 Hz Maximum sound intensity is 95 dBA The hearing was measured at 4 frequencies: 500; 1,000; 2,000 and 4,000 Hz The range of sound intensity is from 0 to 95 dB with scale of 5 dB

- Identification of hearing loss level:

+ Calculating average hearing threshold (PTA) using Fowler Sabine’s formular:

+ Hearing loss level of each ear (%): based on average hearing threshold and Fowler Sabine table

to calculate the hearing loss level of each ear

+ Hearing loss level of both ear:

Hearing loss level (%) = [(hearing loss level of good ear x 7) + hearing loss level of bad ear]/8

- Classification of hearing loss according to Fellmann-Lessing

Result and Discussion

1 Results of measuaring the noise in some working areas of SU-30 aircraft maintenance soldiers

Table 1: Results of measuring the noise in refueling and technical checking places in airport

Refueling and technical

checking places

Sound intensity level dB (dBA) Start Boosting Take off Landing Place 1 105.5 ± 1.7 112.1 ± 2.1 98.6 ± 1.9 85.7 ± 1.8

Place 2 100.5 ± 2.2 115.3 ± 2.3 99.2 ± 2.1 89.4 ± 2.2 Place 3 102.0 ± 2.5 107.2 ± 1.8 101.0 ± 2.4 91.2 ± 2.3

Place 4 98.2 ± 2.3 109.5 ± 2.4 97.7 ± 1.8 89.2 ± 1.9

Place 5 100.5 ± ,7 113.2 ± 2.7 98.9 ± 2.0 92.3 ± 2.6

Place 6 101.5 ± 2.2 115.3 ± 2.5 99.5 ± 2.3 89.5 ± 1.7

Place 7 99.4 ± 1.9 120.0 ± 2.3 97.2 ± 1.8 87.6 ± 1.9

Place 8 103.3 ± 2.4 110.3 ± 2.6 100.6 ± 2.2 90.0 ± 2.4

Hygienic Standard

(3733/2002/Decision- Ministry

of Health)

85/8 h

The sound intensity levels of refueling and technical checking places in airport were very high and higher than hygienic standard The highest were the sound intensity levels when SU-30 aircraft is in boosting period (the range of 107 - 120 dB) The sound intensity levels when SU-30 aircraft is starting were from 98 - 103 dB During taking off and landing the sound intensity levels were lower, however, they were still higher than hygienic standard When SU-30 aircraft is taking off, the sound intensity levels were from 97 - 100 dB and that were from 85 - 90 dB when SU-30 aircraft is landing

Table 2: Results of measuring the sound intensity levels in technical maintenance area

Technical maintenance area Sound intensity level (dB)

Hygienic Standard

(3733/2002/Decision- Ministry of Health)

85/8 h

The sound intensity levels in working places of SU-30 maintenance soldiers in technical maintenance area were also higher than hygienic standard

Thus, almost working places of SU-30 maintenance solders in airport and technical maintenance were polluted by noise, the sound intensity levels were higher than hygienic standard Previous studies also showed that the noise caused by aircrafts was very high Vu Dinh Can et al [1] had measured sound intensity level of MIG-21 aircraft and the results showed that the sound intensity level when MIG-21 aircraft is boosting was 130 dB Pham Duc Nguyen et al [3] had measured sound intensity levels of SU-22 that were from 140 - 145 dB The investigation of Pham Xuan Ninh [4] on noise in aircraft maintenance are showed that the sound intensity levels of this were from 84 - 130 dB

In this study, we have investigated the noise caused by SU-30 aircraft which is modern aircraft, however, the results showed that the noise caused by SU-30 aircraft was very high and that

is a major factor which has impact on hearing and health of soldiers, specially, the aircraft maintenance soldiers

2 Results of measuring the hearing of SU-30 aircraft maintenance soldiers

Table 3: Results of calculating hearing loss according to dB among aircraft maintenance soldiers (n

= 88)

Hearing loss according to dB Number Rate %

The rate of hearing loss in aircraft maintenance soldier was 23.9% in which the rate of minor hearing loss was 13.6% and medium hearing loss was 9,1% The rate of serious hearing loss was only 1.1%

Table 4: Results of calculating hearing loss according to % (n = 88)

Hearing loss according to % Number Rate %

The results showed that almost SU-30 maintenance soldiers suffering from hearing loss were at levels of less than 55% The rate of hearing loss level of 15 - 25% was highest (8%) and the rate of hearing loss level of 56 - 65% was smallest (1.1%)

Figure 1: The rate of hearing loss in different seniority (n = 88)

Table 5: Hearing loss levels in different seniority

Seniority Minor

hearing loss

Medium hearing loss

Serious hearing loss p

< 5 years (1) 2.3 0.0 0.0

p1-3 < 0.05;

p2-3 < 0.05

5 - 10 years (2) 3.4 2.3 0,0

≥ 10 years (3) 8.0 6.8 1.1

The rate of hearing loss among maintenance soldiers with seniority of over 10 years was highest (15.9%) which higher than that in soldiers with seniority of 5 - 10 years and less than 5 years The higher seniority, the higher level of hearing loss in SU-30 aircraft maintenance soldiers

0 2 4 6 8 10 12 14 16

<5 năm 5 - 10

năm

>10 năm

2.3

5.7

15.9

%

We had found medium hearing loss only in maintenance soldiers with seniority of over 5 years and serious hearing loss only in maintenance soldiers with seniority of over 10 years

Thus, the rate of hearing loss among SU-30 aircraft maintenance soldier was quite high (23.9%) Almost previous studies showed that the people exposed to the high noise who have high risk of suffering from hearing loss The study of Nguyen Quang Hung et al [2] had found out that the rate of occupational deaf among aircraft repairing workers, tank repairing workers were 11% and 14.66%, respectively The study of Le Trung and Nguyen Thi Toan [6] was carried out in 11 factories with about 14,000 workers who exposed to the noise of over 90 dB showed that the rate of occupational deaf was 10.94% The study of Pham Xuan Ninh among AN-26 aircraft maintenance workers also showed that the rate of hearing loss among them was 11.59% [4] Thus, working in environment with high noise is the main cause of hearing loss and occupational deaf

The level of hearing loss is proportional to the seniority of soldiers In our study, the results showed that the higher seniority, the higher rate of hearing loss and the higher level of hearing loss That finding consisted with the results of Nguyen Quang Hung’s study [2] to investigate hearing loss among workers in military factories as well as results of Pham Xuan Ninh’s study [4] to investigate hearing loss among AN-26 aircraft maintenance workers

Conclusion

The sound intensity levels at working places of SU-30 aircraft maintenance soldiers in airport and technical maintenance are of Air-base X, Vietnam Air Force were from 85 - 120 dB which were higher than hygienic standard The high noise is the main cause of hearing loss in

SU-30 aircraft maintenance soldiers

The rate of hearing loss among SU-30 aircraft maintenance soldiers was 23.9% The higher seniority, the higher rate of hearing loss and their higher level of hearing in SU-30 aircraft maintenance soldiers

Reference

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