[Ether]

Originally Posted by Al Skierkiewicz

As Ether pointed out, a digital output could make a nice beeper if you couple it to an LM386 or equivalent and a speaker.

Here's another thought:

Could you just connect the tweeter to the RTS or DTR pin of the cRIO's RS232 port and toggle it at a sufficiently annoying frequency? (like perhaps the tweeter's resonant frequency - if it's low enough to hear :-)