It depends on what you mean by loud. I have several s9's and what i found to be a bit annoying is the whine\resonance you hear once the miner stabilizes and starts hashing. I played around with manually adjusting fan speeds and got to a good point. If you underclock the S7 you can reduce the fan speed a bit which should help you out.
I think underclocking is going to be easiest, then look at possible solutions to dampen sound. I don't think you will find fan's with as high of RPM and be quiet, so again underclocking you might be able to look at a different fan. Although that still leaves you with the AP3 it is a good PSU just is in no way quiet (most server PSU's are not).
So you can either look at something like EVGA 1600 in atx (pricey), or go to way's of dampening sound. If your like me it's summer so make sure you really monitor what heat does with your solution. Some cabinet's in summer could be a death trap if you don't get enough air in and hot air out. And this is all before you look into ROI if your doing all this for 1 S7 some solutions are going to be hard to justify cost.
