Its a shame really. Its not really about how loud it is, but the actual sound quality.
A tiny speaker inside a laptop or Virtua boy isnt going to be able to reproduce a good sound spectrum. It will lack bass and full spectrum ability.
In addition, a tiny air chamber made from thin plastic, has no resonance to it... so the sound is again.. destroyed before it even has a chance.
The reason why most arcade machines sound so good, even at low volumes, is that they use a decent sized speaker with the entire hollow cabinet as the air-chamber / amplifier. Take the speakers out of that cab, put them into a small plastic box on a table, and they wont sound half as good.
Now, I cant say for sure what Nintendo used to develop the sound on the VB. But its doubtful that they used the actual systems speakers. As such, theres probably a lot of potential to hear things the way they were actually designed to be heard... rather than the limitations of th
Edit
According to this guy, theres a headphone jack. The sound output is actually much better than the speakers can produce. Have a listen on your home system, decent pc speakers...etc.
-VS-
VB Speakers