Recently I am noticing a whining sound when accelerating mainly at 1st and 2nd gear. What could this be due to ? Here is a link to the video demonstrating the issue:

https://www.dropbox.com/s/tmavi6y0to...84928.mp4?dl=0

 

Hard to tell could be just a noisy power steering pump.
Worst case Sanario could be your transfer case.
What year is your car
How long have you had your car.
When did you start hearing the noise.
My car has a very faint whistle when I give it throttle in park or drive or neutral .
Checked for intake leak found nothing.
Did it in the old tranny and still has slight whistle with the new tranny from mercedes .
Installed by mercedes under warranty.
I only have 16000 plus miles on my car.
12 c300 4matic sport

 

Had this problem for 3 months and started by replacing the idle pulley for about $60, resulting in minor improvement; however it did not go away. Opted to change the next pulley in line; the alternator pulley and have the bearing replaced with local mechanic for about $150....problem went away!