Cognitive radio networks manage spectrum effectively by capability of the usage of correct spectrum management techniques. This is taken in accordance on conformity allowing an unlicensed to use the spectrum channel properly by utilization of the underutilized spectrum. Spectrum sensing determines an agreement of a spectrum hole exists by the imitation of the truth of the unlicensed user. This paper analyse all the important spectrum sensing techniques such as, energy detection, minimum Eigen value detection and matched filter technique and describes the affectivity of the methods. It also represents the energy detection based spectrum sensing and represent their limits and efficiencies. Also the affectvity of additive white guassian method is tested against the noise using number of primary and secondary users.