Thanks for the replies. I played a bit and was able to generate a WAV file and listen to it. However, there are some things I still want to know.
I can play the generated file in VLC, but I can't play it in Audacity or see it's waveform. I'd like to see the waveform to see stuff like noise. I tried to see it in GRC's WX GUI Scope Sink, but I don't know how to make it show the standing waveform (without updating constantly).
I though of using the Head block, but how can I know, in runtime, the amount of items that will be passed?