Crying babies (or lack thereof)

I live in a 2nd floor apartment, and my neighbors below me have a 5 month old baby. I haven’t heard him cry once. I find this very strange, as the walls in this place are not that soundproof.

I know darn well that my daughter (now 3 years old) could make quite the fuss when she had a gas pain at 5 months old.

Does anyone who is professionally knowledgeable about babies find this odd? Or is this perfectly normal?

The mom brought him with her when she came up to introduce herself one night (and subsequently complain that my daughter playing was keeping her son awake) and he never made a sound…

They claim that he is a light sleeper and that my daughter playing in our apartment wakes him up (they’ve complained several times in the last two weeks) but yet, I’ve never heard this baby cry at all. And my daughter hasn’t been making outrageous amounts of noise either.

Does anyone have any insight into whether I’m looney myself for thinking there is something wrong with the fact that I’ve never heard this baby make any noise/cry?

I realize this doesn’t make a lot of sense… sorry.

The babies I’ve known (a total of perhaps a dozen) have shown a huge variation in their general tendancy to cry, and how loud. So you may simply have run across a rather good-natured baby who fusses rather than cries and whose parent attend a bit more closely than is typical.