According to psycho-acoustic data, our ear’s integration time is approx. 250 ms which corresponds to 210ms in Level-Pan Meter Settings/VU Meter(Loudness)/Resolution. Well, more or less.
What was the reason for a default value of 1 sec then? I’m asking because a default behavior of Wavelab’s VU meter is quite slow compare to a traditional VU meter i.e. Wavelab’s VU meter shows a lower RMS level. As consequence it makes an engineer to push RMS higher in mastering.