45:  How do I turn down the bell volume in Emacs running under X Windows?

  You can adjust the bell volume and duration for all programs with the
  shell command xset.
   
  Invoking xset without any arguments produces some basic information,
  including the following:

    usage:  xset [-display host:dpy] option ...
      To turn bell off:
	  -b                b off               b 0
      To set bell volume, pitch and duration:
	   b [vol [pitch [dur]]]          b on