We can measure
LAeq and
LAN of community noise correctly by short interval measurement, if frequency distributions of
LpA are similar to that of by continuous measurement. We measured community noise for 24 hours at 6 sites, and for 1 month at 1 site. And we analyzed hour-by-hour changes and day-by-day changes of frequency distributions of
LpA.
Results of study on hour-by-hour changes of frequency distributions of
LpA are as follows. In daytime, if traffic noises are mainly measured, we can get them correctly by measuring 30 minutes at most. But in nighttime, to get them correctly, we must measure continuously at nighttime, or measure 10 minutes interval every hour.
Results of study on day-by-day changes of frequency distributions of
LpA are as follows. In daytime, we can get them similar to that of by continuous measurement, in a month by 10 minutes interval measurement in a month. But in nighttime, noises propagate through long-distance, then noise levels depend on direction of wind changes day by day. And frequency distributions of
LpA also change day by day. Therefore, it is appeared that we must measure community noise for long interval to get frequency distributions of
LpA correctly.
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