rather weak battery

I do not understand why, but it's been two weeks since I have my samsung note 2 and I notice that the battery discharges quickly.

at 00, he is 100% in the morning to 08H, it is 94% or even 92% sometimes I do not know if the same problem !!!!

end of the day (18h), I'm 50% while I surf 30min the day, and I listen to music for 1 hour.

Do you find this normal ????

otherwise I am satisfied with the Note 2, it's great, but the battery seems weak, then I do not know if I came across a samsung note 2 failed but in any case, I am disappointed because my wife who has an iphone 4 , the battery is not discharged as fast in 1 night .....