Popping sound from sound system
Motors do create a fair amount of electrical noise especially if the blower has a variable speed controller, an RFI filter may help as isherwood suggest or possibly an isolation transformer , in my riding arena we pipe music and I had to use step up transformers at the amp and step down at the speakers to get rid of. Ham radio and 60hz buzz on the feeds that were close to 180' but the poping is probably just motor noise. You could also move the feed for one of the outlets to the opposite leg so they are separated this may be the easy fix.