As wireless devices proliferate, more of these devices have to share a finite and increasingly limited amount of available radio spectrum. Currently spectrum bands are used for a particular purpose that they are licensed for. However, these spectrums are not always used by their licensees or primary users, and as such are unused and are idle most of the time. These swath of unused frequency spectrum can be used by unlicensed users, when available, to mitigate the spectrum scarcity. In this article we study different methods of spectrum sensing in cognitive radio paradigm and compare them in terms of their potential interference with primary users.