(1) Reaction at the exposure of the high noise level of an air craft
We did a noise survey at a primary school near the Osaka International Airport in 1974. We observed children in the play ground from the roof of a school building, they kept playing without any surprise at the exposure of a high aircraft noise of over 100 dB (A).
We set a frame camera on the roof for monitoring them with noise measurement simultaneously. They were playing dodge ball games. We took them in the area A or B in the playground from the school building roof. Their locations are shown in Fig.1 and 2.
We arranged white lines to get the coordinate of the ground while they were not there.
Fig. 1 Play ground and school buildings showing the camera location and the areas monitored
Fig. 2 Elevation of the school building to have a frame camera on the roof
We superposed them and found the moved distances of particular students from two successive frames. From the moved distance one’s velocity and acceleration were calculated. They were compared with the air craft noise simultaneously measured. It is shown in Fig.3.
Fig.3 Moved distance, velocity and acceleration of particular students in the playground at the exposure of high aircraft noise
The moved distance and velocity did not change much with the noise, but the acceleration seems to be decreased following it.
When any huge energy is given, one hears large impact sound. It seems that this correlation is imprinted in our self.
Unfortunately, we could not have time to give them a similar large air craft noise from a different direction on the roof.
(2) Social survey on aircraft noise near the Osaka International Airport
This is a part of the report about the aircraft noise survey around Itami City and adjacent cities near the Osaka International Airport.
Questionnaires for winter time were distributed to 1219 people from Nov. 28, 1972 to Jan. 16, 1973. Invalid answers were 10. For summer they were given from Aug.4th, 1973 to Aug. 31st, 1973 at Itami City and its near areas. They were 2,333 and invalid answers were 6.
The aircraft noise survey was done in 11 cities simultaneously from Nov. 1973 to Jan. 1974. The noise level contours for peak levels in dB(A) with 5 dB(A) interval were obtained as shown in Fig.1.
Fig-1 Contour lines of peak level dB(A) with 5dB(A) interval
Fig-2 Contour lines of WECPNL with 5dB interval
The partial correlation coefficients, which show how strongly each factor is related to the outsider, are shown in Fig.3 which was obtained from the above quantification. The outline of the theory of quantification II by Hayashi is given in Chapter V of my home page www.ecohouse.co.nz.
The difference of seasons, summer or winter, has the second contribution after the factor of peak level. In summer, living condition is different from winter. They tend to open windows and loose sound insulation. Another possibility is that flight courses are different and areas of higher noise level were increased.
Fig.-3 Contribution of each factor (partial correlation coefficient) to annoyance having the factor summer or winter.
Three factors, peak level in dB(A), duration time and the number of flight, were used as factors to affect annoyance, the peak level was dominantly large compared with other two.
The number of flight has a small contribution, because it does not have much difference at the surveyed area.
To eliminate any biased answers to the question of aircraft noise, it was given after prior questions for a living environment. This way of questioning at a social survey is called the OECD method. Questionnaires were given directly on aircraft noise in parallel. The former is called “indirect” and the latter is called “direct”. They were chosen as categories for a factor.
Which has more contribution to the annoyance of an aircraft noise a peak level (in Fig.1) or a WECPNL (in Fig.2) was examined having them in a factor?
17 factors were selected for the quantification and the partial correlation coefficients were obtained in Fig4.
Among factors which affect to the annoyance of aircraft noises, the noise level of averaged peak level dB(A) affects dominantly, namely it has the most partial correlation coefficient.
The contribution of the factor “direct” of “indirect” was not large. It was resulted because all the area was exposed to high aircraft noise. However, their scores not given here showed
Fig.4 Contribution of each factor (partial correlation coefficient) to annoyance with a factor direct or indirect questionnaire
“direct” survey answered more annoyed.
On the partial correlation coefficient, peak level has more contribution than WECPNL.
In such a noise environment, duration time and the number of flight do not affect much and the peak level is enough to express the noise environment.
The experience of noise environment at the former resident has the second largest 0.158 to the aircraft noise rating. It means the factor should be counted at any other noise survey.
The flight course is large with 0.128. It must be caused by the diffraction of surrounding houses.
As peak level dB(A) affects dominantly to the annoyance of aircraft noise, the next discussions are done with it.
Distribution of responses to an aircraft noise
Each block was classified with 5 dB(A) step for the average of peak level dB(A). Annoyance and disturbances of speech inside and outside were converted to the distance scale for their categories. Each answer was estimated on the scale and it was averaged in each block in Fig.5.
Each of the three items is shown in the next three figures. There the correlation coefficient is given. Not only for annoyance but disturbances of speech, the response shows different attitude at the level over 95 dB(A). The 95% confidence interval is given in Fig.6. It has a wide range
Fig. 5 Distribution of annoyed areas around the Osaka International Airport
and covers adjoining categories. It shows that the response to an aircraft noise has wide
distribution.
Fig. 6 Relationship of peak levels vs noisiness
Fig. 7 Relationship peak levels vs speech disturbance inside
Fig. 8 Relationship of peak levels vs speech disturbance outside
Discussions
Answers in summer and winter showed significant difference and they feel more annoyed in summer. They tend to open windows and loose sound insulation. Another reason is different flight courses and areas of higher noise level were increased in summer.
It was shown that a flight course related to adjoining houses affects as well. It was caused by the diffraction and might be affected psychologically if it is visible or not.
It was shown that noise level with peak level dB(A) or conventionally measured WECPNL was dominant to decide the annoyance in this region. However, their partial correlation coefficients were unexpectedly not that large with 0.459 and 0.414. It was caused by the distributions of noise level measurements and individual responses.
The difference of partial correlation coefficients between peak level dB(A) and conventional WECPNL was not much
When we get responses on a noise environment in living environments we have to consider their history of noise environments, other noise sources, diffraction and sound insulation, seasons etc.
Because of the large distribution of responses more objective scale such as the Guttmann scale or a pair comparison might be needed to consider to be used. The measurement of noise levels should not be done on a few days but would need, for instance, a year or four seasons. When noise level distribution in a wide area is measured, enough number of measuring points is needed.