What sound are trying to get your sennie to make? What ever it is, that is the sound he/she needs to hear repeatedly. Try to ignore the sounds you don't care for and show excitement and/or give a treat when he does something you like or want. I always talk to mine when I am with them. When Charley feels like it, she will say "pretty bird". When I respond she will repeat it a few more times.
As for the squeaky sound...WD-40

Charley

Romeo