Relation Between Passby and Stationary Near-Field Noise Measurement of a Passenger Car 785065
Measurements were carried out with a few samples of one type.
Nevertheless, as conclusions are based on a given type or at most
on a group of motor-noisy passenger cars, it can be taken for
granted that conclusions are valid also for a wider range of road
Results of full-throttle acceleration passby measurements are
governed mainly by engine noise, the contribution of rolling noise
being negligible. This means that, as intended, type approval test
can be used only to assess noise emission of a car under relatively
rare circumstances, existing mainly in urban traffic.
The noise radiation pattern of a car in motion can be
approximated in horizontal plane by a circle with acceptable error.
This can be important especially for traffic noise prediction
The noise emission of a front engine car can be approximated by
the results of the stationary near-the-exhaust measuring method
only under operating conditions of fast variation in engine speed,
unless, the exhaust system is defective or utterly deteriorated. It
has been show that~in accordance with the intention of the standard
/3/~the state of repair of the exhaust system can be assessed both
from runup and deceleration measurements. This means that
stationary near-the-exhaust measurements are appropriate means for
Distinct similarity has been found between passby and stationary
near-the-engine measurements when consistent operating conditions
were maintained. This suggests that also some degree of correlation
between the results of standard measurements exists if the data are
restricted to certain types or samples of only one type. The
research work so far performed does not enable for setting up
quantitative formulation of the question.
Fülöp Augusztinovicz, László Veréb, Béla Buna
17th FISITA Congress (1978), Budapest, Hungary