I suggest S5's for areas that sound is not an issue.
he should searching for not only a place where the sound is not an issue, he should find for a place where the temperature is not an issue too, dont forget that
btw about to reduce the noise, there is one thread talking about how to underclock the s5 here -> https://bitcointalk.org/index.php?topic=1151460.0 i know is not what are you searching for, but maybe reduce it a little bit will bring you a reduction of the noise, dunno.
I think the easiest way to solve this is lower the speed of the fan. It depends on how cool air you can blow on the S5 but if you buy box fans and use that to push air through the S5's fin, you should be able to lower the fan by a huge amount even at 30c ambient.
This work well since the box fan has a fairly high CFM but is pretty quiet because of how bit it is.
The second thing is if you can feed it cool air, for example if its cold 8 months per year like it is here, you can just open your window and feed it cool air, assuming its not a window vulnerable to taking in water.
Right now my fans are set to 38% and are thus quite bearable with under 60 dB for all of them combined.
Even if you underclock and lower freq with original fans it's not what I would consider quiet (IE one I would want in a room I use much). Some have switched fans to much nicer and quieter ones that is really needed if you want more quiet not just bearable.
Avalon 4.1's still are king as far as quiet miners that are not to old. But they do cost more to get and only from used market.