LabVIEW
Frequency domain filter to time domain filter
Solved!
If you Google this phrase -> locale variables labview. You will find a lot of useful information on the first page. Then working with locals in Labview, they make copies of data buffers. When you read from a local variable, you create a new buffer for the data from its associated control. If you use local variables to transfer large amounts of data from one place on the block diagram to another, you generally use more memory and, consequently, have slower execution speed than if you transfer data using a wire. So the only advise I can give you, is use them with care. Always have I mind their cons. I think it is wrong, not to use them if they make sense in your programs. But be aware of race conditions.
Also if you have 2 loops running in parallel, both working with same variable. You should consider the Producer/Consumer design pattern.
More about it here http://zone.ni.com/devzone/cda/tut/p/id/3023
Think about your soundcard as 1 AD unit and 1 DA unit. This units are separated so they do not have to know about each other. They actually works best that way. So I would not change any thing in your setup. Then I am working in may lab with soundcard input and Labview, I sometimes listen to music played with winamp. No problems at all. Just remember that it will always be some latency between soundcard output and input. In your case it will be .5 second since you plan to update your sound meter every .5 seconds. But this doesn't matter at all.
