It sounds like the wind hitting a microphone. I have a wireless router not too far from my crack. I tried turning it off, but the problem remained for several minutes after, though it did eventually stop. Would there be a several minute delay after turning the router off? (this is a pain to troubleshoot since it comes and goes on seemingly random occasions.) and I tried already have added that mod Paul, and it did fix a previous issue I had with there being a consistently noisy static sound in the background.