GNU Emacs Lisp Reference Manual

35.15: Beeping

You can make Emacs ring a bell (or blink the screen) to attract the user's attention. Be conservative about how often you do this; frequent bells can become irritating. Also be careful not to use beeping alone when signaling an error is appropriate. (See Errors.)

Function: ding &optional dont-terminate

This function beeps, or flashes the screen (see visible-bell below). It also terminates any keyboard macro currently executing unless dont-terminate is non-nil.

Function: beep &optional dont-terminate

This is a synonym for ding.

Variable: visible-bell

This variable determines whether Emacs should flash the screen to represent a bell. Non-nil means yes, nil means no. This is effective under X windows, and on a character-only terminal provided the terminal's Termcap entry defines the visible bell capability (vb).