PR System One REMstar Auto Filter Cover ?

I've been using a Remstar M series for several years, and it's been very quiet. Just switched to the System One and it's the first time I've ever had the problem of hearing my own inhalations--or the scuba noise, as someone called it. It's driving me nuts. I've had to switch back to my old machine in order to sleep. I contacted Phillips on their website and they never answered me. A nice fellow from an online CPAP store called the Phillips rep for me and asked about a whisper cup, and was told they still do not have one. Obviously they haven't received a sufficient number of complaints, though the guy from the store said he'd certainly heard plenty himself. This machine is useless to me without a fix. The rep said something about using a tabless white filter, so I cut the tab off of mine, but it did nothing. I pirated the filter cover from an even earlier Remstar that was also quite silent, and duct taped it over the filter area, but that did no good either. I haven't tried a rubber mat yet; maybe that will help if I can find one. It really seems like a design flaw. My Remstar M has four square inlets where the filter is, while this one has just the one round one. Maybe that's what makes the difference. I don't get it, but I wish I could figure out what to do about it. Any more suggestions would be much appreciated.