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.