Gurdas,
You are right in what you are trying to do can probably be done without the sound and vibration toolkit. In general, that toolit is geared towards analyzing signals, not producing them. However, I think what you are trying to do can be done with some of LabVIEW's analysis VI's.
One specific VI that might be helpful is the Inverse FFT VI. This VI takes an array of complex FFT data and returns an array of the actual values that would produce such results. In general, when you take an FFT of a signal in the time domain, your result will be an array of amplitudes in the frequency domain (dB vs frequency). However, we typically only think about the real values associated with this calculation. The often forgotten part is that taking an FFT also gives us phase information as well, in the form of complex data. Thus, while we normally view the "real" data, there is a forgotten complex side of an FFT graph that tells us phase information. My point here is that this might be helpful when reconstructing an actual signal from your dB vs Frequency array.
Another option is to simply create a set of sine waves for every frequency specified by your dB vs Frequency array. In such case, you would create an individual sine wave for each frequency in the array, and the ampltude of that sine wave would be determined by the power (dB) at that frequency. You would then add all sine waves together and divide by the total Peak-to-Peak to normalize the graph. I'm not completely that sure that this would work entirely in that taking an FFT of the "created" signal would be the same as the original plot. However, it is certainly worth a try.
Anyway, these are just a few ideas of how you could create a signal based on your original dB versus frequency graph. Once the actual signal has been created in LabVIEW, writing it as a sound file can be done with some of the sound VI's. I hope this helps and let me know if you have any further questions!
Regards,
David Hall | Applications Engineering | National Instruments
