Some pigs are really loud, some pigs are really quiet. I've had both. As long as they are fine and health otherwise, I wouldn't worry about it. I also wouldn't worry if it was consistent behavior, but would worry if a noisy pig suddenly becomes quiet, as that could be a sign of pain or illness.
Out of the two I have now, both are loud... Hadley is quite the wheeker about everything. Sundae doesn't wheek as much, but she 'talks' when you pat her to the point that I will have to turn up the volume on the tv. She has a very distinctive voice... it sounds like someone rubbing a balloon with sweaty hands! LOL! Our previous pig, Linney, was extremely quiet, so my poor husband is still getting used to Hadley. I think my neighbours can probably hear Hadley sometimes! LOL!