From http://www.babycenter.com :

“If your baby’s making rude noises, don’t blame your neighbor’s preschooler. Most 5-month-olds delight in adding new sounds to their repertoire, and blowing a raspberry is a perennial favorite. In fact, he may love it so much that he’ll do it over and over again. That’s normal, too. Most babies master one skill before they move on to the next.”

hm.. nice baby and funny age.. 😀 it’s true.. Allahu Akbar..