You know when you want a player hearing a beep must include an ' \a' into a 'send_to_char' or  a 'ch_printf ' function;  something like this:
send_to_char("Be careful, %s! \a", victim);

Well, if you are tired of the tipical beep sound, or decide to include
some different warnings, you can change the '\a' by:
\33[10;freq]\33[11;length]\a\33[10]\33[11]
where freq is the frequence in hertzs of the sound, and length is its duration in miliseconds.
An example:
send_to_char("Be careful, %s! \33[10;800]\33[11;400]\a\33[10]\33[11] ", victim);

IMPORTANT: If you don't write the last section (after the \a) you'll have change the beep sound in your console ;)