In /usr/local/fop2/fop2.cfg adding the 'q' modifier to either spy_options or whisper_options should remove/silence any announcement, not only the beep. If you still hear that, my guess is that the option was not set correctly in fop2.cfg or fop2 was not restarted after changing it.

If you have a very old FOP2 and a recent asterisk, then you might have some issues with options delimiters. Check the "force_parameter_delimiter" option in fop2.cfg. If you have Asterisk 11 or higher, it must be set to "," if you have really old asterisk then you might need to change it to "|". Either way, FOP2 tries to determine the version and set the delimiter correctly, you can override that detection uncommenting this.