I'm really glad that @ZYOng responded -- I presume he was able to open at least one of the VIs you posted. Sadly, even though you attached something in response to my request, I am still unable to open it. This time, it didn't tell me that the file was of a newer version of LabVIEW (which was the problem with the first two of your attachments) -- it just hung, showing me a partial Front Panel and then a red "Close Window" control in the upper right hand corner -- oops, it just loaded after about 3 minutes ...
So there are a number of problems with your VI. As it happens, I recently wrote a VI whose responsibility was to generate a sinusoidal waveform with a frequency of 2800 Hz that would play for 0.3 s. Like you, I generated this as a Waveform and then played out the Waveform as an analog output through a USB-6212 driving a small audio amplifier (connected to a speaker).
There are two parts. One is generating the waveform. I chose a frequency of 14000 Hz (which is 5 points per cycle, pretty lo-fi, but adequate for my needs), so I need to generate 2100 samples at 2800 Hz to get a 0.15 s waveform when played at 14000 Hz. So now I have my sound wave.
When using NI's DAQ hardware, you need to remember that DAQ devices frequently have internal clocks that are far superior to the timing functions in LabVIEW (not the least because PCs running Windows have no "dedicated" clocks -- the more you do (in parallel) the slower the code runs.
The next thing you need to learn (maybe you should read "Learn 10 Functions in NI-DAQmx and Handle 80 Percent of your Data Acquisition Applications" -- find it on the Web) how to handle DAQmx for reading and writing Waveforms. You need about four DAQmx functions: a DAQmx Create Channel (where you find the DAQ device and say you want to do a AO Voltage), a DAQmx Timing function where you set the sampling frequency and number of points in your Waveform, then when you want to play your sound, do a DAQmx Write Analog Waveform (1 Channel, N Samples), followed with a DAQmx Wait until Done and Stop Task. "Beep".
Your VI generated a Waveform (many samples). You send it to a DAQmx Write, but say "1 sample", though you generated 20,000 samples! You also have a Wait (to clock the speed of the loop) with a Wait time of 0 ms -- what does this mean?
Do study the examples that ship with LabVIEW. But you might also try to understand how I generated my little "Beep" and see if you can duplicate the ideas I mentioned in your code.
Bob Schor
