Reliable detection of other wireless systems is crucial for the systems that share the same frequency band. In wireless communication channels, there is uncertainty in the received signal level due to multipath fading and shadowing. Cooperative sensing techniques in which wireless stations share their sensing information can improve the detection probability of other systems. This paper presents the field trial results of a cooperative sensing scheme with energy detection and hard decision cooperation. The results demonstrate that the cooperation of wireless stations can relax the stringent sensitivity requirement of energy detection.