Noisy fan after replacement,

I bought a generic chinese fan for this labtop and it makes a much higher pitched noise than the original Panasonic. Is this an installation issue or are these fans really of poor quality. If I move the computer around sometimes I hear it even rev down and stop then start up again. The pitch is also much louder than the original Panasonic one.

Anyone know a good fan for this or should I try to find an original one from a broken computer? Also would replacing the heatsink unit help with heating?