Q. Why do we make a noise on Purim to blot out Haman’s name? There are other villains in the Bible, e.g. Pharaoh, and we don’t hiss or boo when they get a mention.A. Haman is singled out for special treatment because of his links with Amalek.
The Torah reading on Purim (Ex. 17:8-16) says, Timcheh et zecher Amalek, “erase the memory of Amalek”, and during the Megillah it is customary to try to blot out the name of Haman whenever it is read.
The resulting exuberance sometimes gets out of hand and in some synagogues they try to control it by methods such as holding up a sign that says “Sh!”.
Symbolically blotting out Haman’s name was already known by Rashi in the 11th century. At various periods, attempts were made to blot out the custom itself, but the Rema (Moshe Isserles) wrote in the 16th century, “We should not nullify any custom or deride it” (note to Shulchan Aruch Orach Chayyim 690:17).