Having worked on this a/c whining issue with Lexus Santamonica, the technician who came to my work place to ride the car with me to see if we can recreate this scenario mentioned about a new fix that Lexus found for a particular problem in the a/c high compressor valve (detailed below)
"At about 1200-1400 rpm when accelerating the car from a signal/stop, this whining sound starts in the a/c and once we cross the 2000 rpm then the sound stops. Again when we brake and decelerate and when the RPM is around 1200- 1400 the sound starts and stops once we go down below 1000 RPM. "
After i took this cue from this technician i tried to drive my car in the 1200-1400 rpm which is what it will be in when ur driving on surface roads at 35-45 miles/hr speed, i heard this whining sound and then it disappeared above 2000 rpm and the reverse happened too. So now i hv called up the service center and hv talked to the technician and we have setup an appointment for next tuesday for this problem to be fixed. will update all of you guys after that.