Happens with me too, plus sometimes I hear screams if any player takes dmg or jumps or runs.
As far as I am aware, both are client-sided SA:MP bugs and we can't really do anything to fix them.
The bug LPCOLTER has shown is determined by the CJ weight mechanics; if your health is already full and you eat or use vending machines for a while (only the machines matter in our case since the interiors with food are disabled on the server), you might turn obese, as everyone else on your screen. Whilst other players will still be able to move normally, your obesity won't let you run as long, fast and climb as high. The only way to fix it is to replace the default vending machines with the serverside scripted ones which wouldn't inherit the aforementioned mechanics, but I don't think that it's worth that.
The 'baby sound' bug is caused by the incorrect sound pitch modification which was apparently scripted inaccurately by the game developers.
Relogging fixes both of the bugs.
