Why is the hd video not clear on my camera?

My camera is 3 months old and i have never used video recording on my camera which is capable of capturing 1080 p HD video at 24 frames per second. but yesterday i gave a try by recording a scene for 2 mins using Sandisk Extreme class 10 4gb SDXC card.

When i uploaded the video to my computer, i found lot of noice (not the background voice) within the video quality. Is the camera defective or is it something very common. I doubt that 1080p video should be crystal clear. Shall i contact NIKON for this?