The paper uses sets of experimental data, concerning commercial
vehicles, to study the correlation between pass-by and stationary
noises through measurements executed according to external noise
standards. We consider two sets of experimental data: before the
new legislation (higher levels) and lower levels satisfying the new
limits in Brazil. In addition we calculate the Loudness in sones,
from the octave band spectrum, and compare the results with the
usual evaluation in dB(A), with the purpose of emphasizing the
qualification besides the quantification aspects and promoting
conditions for people understanding.
We have applied Brazilian standards which are technically
equivalent to their correspondent ISO 362 and ISO 5130. Some points
regarding the application of these standard are in discussion since
the last few years, as follows: The application of ISO 5130 in
circulation vehicles and its correlation and meaning when compared
to pass-by noise. The existing empirical expressions relating noise
measurements in semianechoic chambers with pass-by noise; The
improvements and restrictions relative to equipments, test
conditions, test parameters, sound pressure level limits, more
refined acoustic solutions..., but still maintaining the same
parameter for evaluation; The modern addition of acoustic
qualification to the usual acoustic quantification; The engagement
of society with ecology and the difficulties of people to
assimilate a logarithm scale like dB(A).
The paper is divided into two parts. The first tries to find
some correlations among the parameters used in the above standards,
and the second part concentrates as a target to show the polemic
questions we have today continuing to use an old parameter like
dB(A) for evaluation instead of a more complete concept as the
Loudness.
The discussions, conclusions and recommendations are supported
by spectra profile, regression curves and graphics taken from the
measurements effectuated involving the chosen parameters.