Compared to ALL other unmodified power supply units I have used, the Seasonic SS-300FS is about the quietest. These other units include 2 models of Enermax, SH, Zalman and many generic power supplies. Despite the slightly quieter noise level of the Zalman ST-300BLP, my sample's rapid speedup to a much higher noise level makes it significantly more intrusive than the Seasonic, overall. As mentioned before, this is the same behavior observed in the Enermax and SH models, as described in detail in my previous PSU articles. The new Antec True Power PSU appears to suffer the same affliction.