Hey you know Cape Town okes.....they bark at anything!!!
It can happen if the points are not set quite right and timing is out a bit leading to the coil sending a false signal to the hollow input shaft which then makes a loud growling noise.
This is normal for anything with pistons.
OH????? sorry....a 206.....ooookkk.....If its not a piston engine and it does it more than once... send it to maintenance. Check the compressor out for wear and tear....and...don't expect me to fly it there over "the Mountain" either.