erc-beep-match-types

erc-beep-match-types is a variable defined in `erc-match.el'.
Its value is

(current-nick)

Documentation:
Types of matches to beep for when a match occurs.
The function `erc-beep-on-match' needs to be added to `erc-text-matched-hook'
for beeping to work.

You can customize this variable.