Instructions
Press the tilde key (~) on your keyboard to open the developer's console. This can be done at any time in-game, but you may wish to do this on the main menu.
Type "alias "X" "voicemenu Y Z"" where "X" is the name you define for the alias. Replace "Y" with the first key you must press to access the menu, and replace "Z" with the second key you press to use the command. For example, to create an alias for the "Go Left" command, you may type "alias "goleft" "voicemenu 0 4"" and press "Enter."
Bind the key. Type "bind "X" "Y"" where "X" is the key you want to bind the menu to. Replace "Y" with the name of the alias you defined. For example, to bind the previous command to the 4 key on the number pad, type "bind "KP_LEFTARROW" "goleft"" and press "Enter."
Repeat Steps 2 and 3 for the remainder of the voice commands you use most.