Definitions;
TDP - Refers to the maximum amount of power the cooling system in a computer is required to dissipate.
The Asus laptop you mentioned has an ultra low voltage CPU with a TDP of 10 watts, the 13 inch Macbook Pro CPU has a TDP of 35 watts.
The Macbook Pro needs 350% of the cooling capability than the Asus (250% additional), and this is done with a faster (and thus noiser) fan.
Edit: Not sure the % is correct, but you get the point.
Edit2: Couldn't sleep, the thought of incorrect percentage had to be fixed.