As mother of 3 children, I can understand you concerns. Babies love the sound of their own voice, and they love the reactions they get when they squeal. There isn't much you can do, although I found with my older son (who is now 10.5 years), if I squealled at him louder, he quitened down, as there was someone else louder than him. This also worked for my daughter (now 8 years), and is currently working for my 7 month old son. This can be hard to do whilst shopping though, so just ignore his squeals, but keep on talking him. Enjoy his squeals while they last, as they grow up and start talking non stop all too soon, and you wish for the days of the baby squeals again. Good luck!
Mother of 3, Qld