When you were about 4 months old until the present day, you would make sounds with your mouth. I think the sounds you are making were things you heard before you were born. You make engine sounds but the engine is not like my car, it is more like the diesel engine on present day buses. The engines make 3 distinct sounds, a "flappering" sound when they are idle yet running, a high pitched sound when the bus is excellerating and the low pitched sound when the bus is slowing down. You weren't on the bus much after you were born, you make all three sounds and alternate them in the same order as the bus. I think you also make the sound of your mum's intestines because your head was close to her organs. Human intestines make lots of small farting sounds that can't be heard from outside the body. You also do that with your mouth, a farting sound.
I could be wrong about everything though, you may just be making those sounds.
