JOURNAL OF MILETRRV PHRRMRCO-MCDICINC 7-2013
STUDY ON THE EFFECT OF NOISE ON THE HEARING OF SU-30 AIRCRAFT MAINTENANCE SOLDIERS
Nguyen Minh Phuong*; Nguyen Van Chuyen*
Nguyen Van Ba*; Nguyen Tung Unh*
SUMMARY
SU-30 aircraft is a modem 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.
i N T R O D U C T i O N
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 woriters have to wori< 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 modem 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.
* Vietnam Military Medical University
Address correspondence to Nguyen Minh Phuong: Vietnam Military Medical University E.mail: [email protected]
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JOURNRL OF MILITRRV PHHRmflCO-M€l>IC1N€ 7-2013
Some places were measured sound intensity level as followed-
+ Refueling and tedinical checking places during preparafion for taking off and landing.
+ Tedinical 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:
- Measunng 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:
p-p^^ dB(500) + dB(1.000) + dB(2,QO0) + dB(4,00Q) 4
+ Hearing loss level of each ear (%):
based on average hearing threshold and Fowler Sabine table to calculate the hearirig 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 ear1/8.
- Classification of hearing loss according to Fellmann-Lessing.
RESULTS 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
Place 1
Place 2
Place 3
Place 4
P l a c e s
Place 6
Place?
Place 8
Hygienic Standard (3733/2002/Decision- Ministry of Health)
SOUND INTENSITY LEVEL dB (dBA) Start
105.5
±1.7 100.5
±2.2 102.0
±2.5 98.2
±2.3 100 5
±.,7 101 5
±2.2 99.4
±1,9 103.3
±2.4 Boosting
1121 ± 21 1153±
2-3 107.2 ±
1.8 109.5 ±
24 1132±
2.7 115.3 ±
25 120.0 ±
2.3 110.3 ±
2.6 Take
off 98-6
±1.9 99 2
±2.1 101.0
±2.4 97.7
±1.8 98.9
±2.0 99.5
±2,3 97,2
±1.8 100.6
±2.2 Landing
85 7 ' t 1 8 89.4 ±
2-2 91.2 ±
2.3 89.2 ± .
1.9 92.3 ±
2.6 89.5 ±
1 7 87 6 ±
1.9 90.0 ±
2 4 85/811
JOURNRl OF MIUTRRV PHRRMflCO-MCDKINC 7-2013
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
Technical room Maintenance place
Outside Hygienic Standard (3733/2002rt3ecision-
Ministry of Health)
SOUND INTENSITY LEVEL (dB)
99 8 ± 1 4 100 7 ± 2 . 3 98 3 ± 1 . 5
85/8 h
The sound intensity levels in worl<ing places of SU-30 maintenance soldiers in technical maintenance area were also higher tfian 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 Due Nguyen et al [3] had measured sound intensity levels of SU-22 that were from 140 - 145 dB. The investigafion 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 modem 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 annong aircraft maintenance soldiers (n = 88).
HEARING LOSS ACCORDING TO dB
20 - 40 dB 41 - 60 d B 61 - 80 dB
> 8 1 dB Total
NUMBER
12 8 1 0 21
RATE %
13.6 9.1 1.1 0.0 23,9
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 %
1 5 - 2 5 % 26 - 3 5 % 36 - 4 5 % 46 - 55%
56 - 6 5 % 66 - 7 5 % 76 - 90%
9 1 - 1 0 0 % Total •
NUMBER
7 5 4 4 1 0 0 0 21
R A T E %
8,0 5 7 4,6 4,6 1.1 0.0 0.0 0,0 23.9
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JOURNfll OF miUIRRV PHBRMHtO-mtPICINe 7-2013
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 66 - 65% was smallest (1 1%),
< 5 years 5 - 1 0 years > 10 years
Figure 1: The rate of hearing loss in different seniority (n = 88).
Table 5: Hearing loss levels in different seniority.
SENIORITY
< 5 years n, 5 - 1 0 years ^i a 10 years (3) Total
MINOR HEARING
LOSS 2,3 3 4 8 0 1 3 6
MEDIUM HEARING LOSS
0.0 2.3 6 8 9.1
SERIOUS HEARING LOSS
0,0 0.0 1 1 1,1
P
Pi-a<
0.05, P M <
0,05
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. 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 canied 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, woriting 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 wori<ing 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.
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JOURNRl OF MIUTRRV PHARMRCO-MtDICINC 7-2013
T h e rate of hearing loss among SU-30 aircraft maintenance soldiers was 2 3 . 9 % . The higher seniority, the higher rate of hearing loss and their higher level of hearing in S U - 30 aircraft maintenance soldiers.
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1990, tr,3-19.
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