My computer (Dell XPS8300) has been making a revving noise, which is off and on about every 10 minutes or so. I have cleaned all the fans, airdusted etc. no change. I think it's the PSU fan but am not sure now. Recorded noise: http://picosong.com/knwP/ If anyone recognizes the noise, please let me know. If it is the PSU fan, does it need replacing asap?