If you have very good airflow blowing into the PSU, there is a good chance its own fan doesn't need to turn on as SX500-LG is 100% temperature based. Did you try stopping the 120mm case fan to see if the PSU fan would turn on then? These are the noises produced when the voltage is raised by fan controller near PSU fan's starting threshold. As discussed previously, this is unavoidable with a temperature based fan controller as used in the SX500-LG. However, every PSU may exhibit this noise slightly differently depending on the environment it is used in and also due to product variances. Thanks for sharing your experience and being patient with us throughout the process. We will continue to improve and speed up the communications. In your circumstance, the misunderstanding from our distributor was due to their personnel change. Obviously I can't reveal exact sales and return numbers, but the RMA percentage aren't anywhere near that high. We are normally very concerned when anything approaches 1% and the SX500-LG was never there. This thread on Hardforum, however has now become the place to go for customers worldwide to share their SX500-LG troubles so it does contain what appears to be higher percentage of complaints. With that said, we are still monitoring the situation and trying to build a case to possibly release an alternate version of SX500-LG without semi-fanless function. I got our PSU product manager to side with me last year and brought up the idea of removing semi-fanless function with executives but was unsuccessful because we simply had so few returns/complaints to make the case. Semi-fanless in many regions is considered a positive asset so we will probably go at it again this year but instead of trying to change SX500-LG, we'll push to release another version. So for current SX500-LG owners here, what would you like to see changed or updated besides semi-fanless?