Following any Cold start, after about 10 seconds I'll hear a noise from the back that almost sounds like either Speaker Static, or Forced Air from a VENT. I've confirmed its neither. All I can say is its a deep low end static noise very similar to an AM radio on stattic. After I start the engine, it takes about 10 seconds, then the sound fades in quickly like somebody's turning up a volume ****. I've googled it and found several posts on a similar issue from others, but none of them found the cause.