My 4 month old baby boy used to coo & babble when he was 2 months old. he is quieter now & occasionally makes raspberry noises. he smiles & laughs. he also has good eye contact & follows objects. he loves playing toys but no noise. is this normal?

Difficult to determine from just this description. He should be due for his 4 month well child check at which time the Dr will fully examine him includig his neurological/developemental status. Make sure you bring your concerns to their attention so they are aware.

A follow up with your Pediatrician is recommended at 4 months. Does he respond to your voice and sounds? If not, inquire about a hearing test. Reading to your child will help to develop verbal skills during infancy.