Mine does the same, has done for years.
Once, I was away, volunteering on a camp, the Children were in bed, the adults up de-briefing. One of the supervisors suddenly got up and rushed outside, everyone was on high alert. He came running back in saying he swore he heard a car outside on the gravel, everyone agreed . . . . . I sheepishly had to admit, that it was just my tummy!!
For me, it's normal and not serious, but if it's a change for you, speak to your GI about it!