Do you have a relief valve at the compressor itself? If you can open that, or disconnect an airline at the compressor, and the noise remains the same, your problem is not some kind of blockage in the airlines.
That's a good idea. I don't recall there being a relief valve of any kind though. I wish I was at home today. I just didn't have the time to go inspect anything, but I could see from the house that it was still pumping air at least. I will be antsy through the day wanting to get home and check this thing out.
