Here is a bind you can type into console that will help in that situation. Lin mentioned it might be possible to combine two binds I was using, one for displaying my current location and the other an audible sound file asking for help. Within a few minutes I was able to figure it out. Here is a single bind that will let your teammates know your current location followed by an audible "I need backup" and or "Get over here and help me".
Type the following command in console making sure console is enabled* If your game is on the same computer as this forum then simply copy paste it into console.
bind "key" "voice_backup; say_team %l"
*** Important, replace key with what ever hotkey you choose to use as a bind. ***
Once you press the designated hotkey it will appear in game as such...see attachment. The bind displays both a current location to teammates and an audible (voice) sound file. If they don't see it perhaps they'll hear it.
*Enabling console...
Press the ~ (tilda) key on your keyboard, the console should appear, if not you'll need to enable it. To do so start game and go to Options>Keyboard>Advanced and put a check mark where it says Enable developer console.
Hope this helps, see you in game...