日本における航空機騒音問題
理事長 五 十 嵐 寿 一
昭和59年3月19日〜21日、中華民国・台湾台北市で、汎太平洋国際空港会議が行われた。
以下はその会議における招待講演の要旨である。
INTRODUCTION
To the general pubilic, deeply concerned with the environment, aircraft noise is a major problem. It is a big problem within the aviation industry and among airport. Although noise had long been recognized as an impact to the aviation, reduction of noise was usually assigned a much lower priority than other factors such as speed, payload and cost until nineteen sixties.
In 1969, the aircraft noise conference was held by ICAO, at Montreal in CANADA and international standards and practices on aircraft noise abatement were published. They include methods of measurement and evaluation of aircraft noise, aircraft noise certification and a noise exposure index for land uses around an airport. The noise certification procedure published by ICAO has played an important role to reduce aircraft noise. Even though a payload of aircraft increased recently, noise level of an individual aircraft decreased considerably, 20dB or more, it means that the sound energy radiated by aircraft reduced to one percent compared with that of old jet aircraft. Based on the ICAO procedures, aircraft noise abatement has been carried out in Japan.
HISTORY OF AIRCRAFT NOISE PROBLEMS IN JAPAN.
Complaints for aircraft noise were raised at the first time in 1955 around airbases in Japan, and sound proof of schools and hospitals was enforced by the government.
In about 1965, jet aircraft were introduced instead of propeller driven aircraft to the civil aviation. Then, many complaints were raised from neighbours around Osaka airport, because Osaka airport is surrounded by 8 cities.
Social survey and measurement at noise sensitive areas were carried out by the noise abatement committee of Osaka city.
In 1971 noise contours around Osaka airport were figured, based, on the measured data at 170 points and compared with those calcurated from the basic data supplied by FAA. They agreed fairly well as shown in Fig. 1. (a),(b). (Ref.1)
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Fig. 1. ECPNL contours around Osaka airport. (Ref.1)
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In the same pariod, rapid progress of industry produced many kinds of pollutions. Considering these circumstances, the Congress enacted the pollution act in 1967.
It mentioned that the government should protect the health and living environment of general citizen. The committee on noise was established in the government and national standards on “road traffic noise”, “ aircraft noise” and “high speed railway noise”were requested to be published.
As to the aircraft noise exposure index, an unit of WECPNL was adopted, refered to the ICAO recommendation. At the time of ICAO noise conference, there were many indices for noise exposure around an airport, such as, NNI (Noise and number index) of Great Britain, CNR(Composite noise rating) or NEF(Noise exposure forecast) of United States, etc . It was discussed at the meeting to unify these units and ECPNL (Equivalent continuous perceived noise level)and WECPNL (with time of day weighting) were recommended. They were also proposed by ISO (International standared organization) in 1977 ,but ISO adopted Lpneq instead of ECPNL. ECPNL is based on EPNL (Effective parceived noise level) of an individual aircraft and it is calculated by integrating and averaging the sound energy of succession of flights.
N : number of flights per one day
T : time period of one day in seconds
In the national standard on aircraft noise, however, Japan adopted an approximate method for evaluation of ECPNL, because noise is usually measured by a sound level meter and its unit is dB(A).
From the statistical survey EPNL can be approximated by adding 13 to the maximum level of flyover noise in dB(A), and WECPNL is modified as,
| N1 : number of flights during |
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07-00 --19-00 |
| N2 : |
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19‐00‐‐22‐00 |
| N3 : |
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22‐00‐‐07‐00 |
Then, (WECPNL-13) is equivalent to Ldn (day and night level) except evening penalty. Based on the modified WECPNL, the guideline of the desirable environment around an airport was proposed by EPA (Environmental Protection Agency), Japan.
in 1973.
WECPNL 70: |
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residential area |
75: |
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commercial and industrial area which are nearly equivalent to Ldn 57 & 62 respectively. |
Recently, in the United States, Ldn has been used as a measure of environmental noise including land use planning around an airport.
PROCEDURES OF AIRCRAFT NOISE ABATEMENT.
The noise contours of WECPNL were delineated for each airport and several countermeasures have been implemented.
(1) Introduction of noise certificated aircraft.
Control of noise at the source is a basic concept of noise control.
Fortunately, since the introduction of noise certification by ICAO in 1969, big progress has been achieved for control of aircraft noise. At Osaka airport, the introduction of airbusses instead of old jet aircraft improved the noise figure about 5 dB. In Osaka however, a number of flights of jet aircraft has been limited to 200 per day in order to avoid the increase of noise impact.
(2) Modification of flight procedures. (Ref. 2)
Modification of flight procedures is an another way to reduce the noise impact to the surrounding areas.
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(a) Steep ascending profile with maximum take off thrust up to an altitude of 1500 m, is applied to most of airports. |
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(b) Cutback profile is applied for special airports which have sensitive areas near airports. Fukuoka and Kumamoto |
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(c) Delayed flap is recommended for all airports. |
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(d) Preferential runway utilization. Tokyo, Matsuyama, Hiroshima, and Sendai. |
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(e) Preferential flight track, to avoid the noise sensitive areas. Tokyo. |
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(f) Night curfew. New Tokyo, Tokyo, Osaka and Fukuoka
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(3) Aircraft noise monitoring.
WECPNL is calculated from the basic data issued by manufacturers for each aircraft type, and it is necessary to check the noise contour by measuring WECPNL of daily operations at several points. Most of the airports have fixed monitoring points and noise data of aircraft are recorded and accumulated to calculate WECPNL. Aquisition of data is usually performed by automatic recording systems, and they should have a function of discrimination of aircraft noise from other noises in the environment. Several techniques have been developed and applied to the monitoring system;
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(a) setting the threshold level of noise and specifiedduration time of flyover noise. |
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(b) discrimination of a noise source in flight from other sources on the ground by corre lation techniques. The road traffic noise can be excluded (Ref. 3) |
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(c) determination of the position of aircraft at a specified space section, using noise data at two positions, (Ref. 4) |
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(d) identification of an aircraft type in flight. In the monitoring system, an information on aircraft types is sometimes required and development of a new technique using acoustical recognition method has been under way. (Ref. 5) |
(4) Zoning and Land Use.
Based on the predicted WECPNL contours around an airport, purchase of lands (within WECPNL 90) and sound insulation of houses (with in WECPNL 80) have been implemented since 1975. The budget of these countermeasures of the government is shown in Fig. 2. In the figure, hatched portion of bars is the budget for Osaka airport.
(5) Construction of a new airport. Reflecting serious environmental problems around Osaka airport, the construction of a new airport was discussed in about 1970, it was planned to build it in Osaka bay at about 5 km off the coast of the main island. Several plans were investigated from the points of technical and economical feasibilities and also protection of environment.
After detailed survey, the location of the airport was fixed near the coast of Wakayama in the south part of Osaka bay. The construction will start soon, and a new airport wilｌ be opened at the beginning of nineteen nineties.
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Fig. 2. Budget for land uses & insulation of houses.
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REFERENCES.
1) J. Igarashi & G. Nishinomiya: “Determination of the noise exposure around an airport.”
Inst. Space & Aeronaut. Sci. Univ. Tokyo, Report. No.476, 1972
2) Annual Report of Ministry of Transportation.
(In Japanese) 1983
3) T. Ono, M. Okuda, I. Ono & N. Hayashi: “Aircraft noise monitoring system with identification by correlation technique.”
Proc. Inter-Noise 79, 1979, 721〜724
4) G. Nishinomiya, F, Sasaki, S. Furukawa, M. Okuda, I. Ono & N. Hayashi.: “Aircraft noise identification system (Application for inflight position detection”
Proc. Inter-Noise 80 1980 1121〜1124
5) I. Yamada, S. Shimizu, A. Yokota, M. Yamashita & T. Okamoto: “Acoustic recognition of aircraft types in flight”
Proc. Inter Noise 83, 1983, 827,830
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