Where is the source to make noise when Haman's name is read from the Megillah?
The Rama 690:17 brings the Avduraham who brings the minhag(a minhag one should not make fun of) of banging during the megillah which initially started outside of reading the megillah(little children writing hamans name on a shoe and stomping).
The Ben Ish Chai hilchos purim 10 brings the Yaavetz who quotes the minhag of his father to bang by Haman,but the Ben Ish Chai notes in his city they only banged by the first and last haman.
The Chidah in Machzik Bracha Kuntres Achron 687 writes that he saw a ksav yad of the Kaf V'Naki who writes the reason why Jews bang and make a lot of noise on purim is for the nations to see and hear what is going on,and when they investigate they will be reminded of the story of purim. This reminds them not to start up with Klal Yisrael because the end result isnt pleasant for Klal Yisrael's enimies.