Power on noise slower than before

when i first got this computer..(15 inch Macbook Pro late 2011 (will make 2 years old on christmas)) when i would turn it on it made this robotic noise as if the hard drive and/or fans were starting very fast then the classic power on intro sound of apple (the piano?) but before the intro the robotic noise is deeper and slower?

what does this mean?

is my memory getting filled?