This is actually quite common in newborns since their digestive system is still maturing, so the growling sounds are usually just the gut getting used to processing milk. My girl had the same thing around that age and our PD said as long as baby is feeding well, gaining weight, and not unusually fussy or gassy, there is generally nothing to worry about. That said, if you notice baby seems really uncomfortable or is crying a lot after feeds, it is worth bringing up at your next polyclinic visit just to rule anything out. The one-month check is coming up soon for you anyway, so good timing to mention it to the doctor then.