2009 Honda CRV Honda CR-V high pitch noise for 15 seconds a

I have a 2009 Honda CR-V and noticed after pulling into a quiet area to park, like the garage, you hear a high pitched noise (like 60 cycle hum) for about 15 seconds then it quits. Found if you have the car off and just turn the switch to ON you can also hear it for 5-6 seconds if motor was warm. Narrowed the noise location down to something near the throttle body. Then found with the switch only in ON and car off, by pushing on the gas pedal the noise would go off and on and then be solid again when you took your foot off the pedal.
Know of one other new CR-V owner at work and she checked and had the same symptoms. Went to Honda Service and after 2 dealers finally found one that went and listened to several 2009 Honda CR-V's and found they too have this high pitched hum. He asked a service mechanic who has noticed that for sometime and said he thinks it is the "idle air control" valve and that is normal. Sounds logical since that seems to be where the noise is coming from, but did not know they made any noise when you turn a car off or have had it off and only turn the switch to ON?
What do you think?