What type of signal are you sending the analog output? You would need to send it something like a sine wave in order to get a sound to generate. If you are using a sine wave (or similar) already then ow have you got the BNC outputs hooked up? Are they hooked up to an amplifier before they go to a speaker?
There are a few things you can look at to see what is going on. First, you should likely be using the “PCI-6229 DO” block to send out your signal. This should send out roughly a 5v signal.
Next, you can use an xPC Scope block hooked up to the signal you are sending into the digital output block to check what you are sending the block. If what you are sending the block looks like it should generate a 10ms square wave then your final check is to use an oscilloscope to verify that the signal is going to the connection you think it is.
If that still doesn’t seem to be working please let us know and we can try a few more things.