Study on the behavior of road vehicle noise emission related to regulation effects noise generation levels and yearly changing noise levels

摘要

In Japan, the National Environmental Agency has been taking road vehicle noise reduction measures for Automobiles (as s unit), with its engine system noise being lowered to its technical minimum. the I-INCE working party states that the unitary automobile noise regulation shows less definite effect of noise reduction. In a test, the noise level at 50cm from the muffler is examined by the measurement at the time of the speed test of the car inspection. In the paper, we verified the said effect of noise reduction by using the above mentioned test results of over 10 years and compared them to their field tests run for a periodical, regulatory inspection of owned automobiles.