I'm sure there are going to be many different answers to this question. My two cents is that, of all the HMPE fibers, there isn't a "quietest". Some bows, some setups, and some shooters seem to "prefer" different ones, and all of the current fibers are considered the quietest to someone out there.
To add to that mix, often times a shooter tries a new material in a string made by someone else than the string they are comparing to-I'm persuaded that the construction of the string has as much (maybe more) to do with it as the material does.
IMO, dyna (97 and 10), 8125, Astro, Excel, 452, etc. are all excellent materials that can be very quiet.