I dont think there is any 'normal' when it comes to things like walking and talking - all kids are so different. I was worried about DD about the same time when she wasnt talking - but I think she was one of those babies that watches everyone and doesnt try until she knows she can do it right lol - she started talking about 18months properly.

I can remember when she was about 18months and she was still only saying one or two words at a time - I put her down for a day sleep and started listening at the door when I heard her talking and she was talking like crazy in there by herself lol trying to sing 'round and round the garden' on her hand - I was shocked!! lol

So try not to stress - the more you talk to him the more he is listening and that's how he will learn to talk - he is just making you sweat it out a bit more lol