Detection of unknown and weak signals has become a study of particular importance as a consequence of the ongoing development in digital sensing technologies. Among well-known methods, the one most commonly used is energy detection. In this paper the efficiency of the conventional energy detection is compared with the efficiency of the recently proposed, so-called stable field detection. The comparison concerns pseudorandom, additive white Gaussian noise (AWGN) produced in the simulation experiment and real radiofrequency (RF) background noise measured in industrial, scientific and medical (ISM) band transmission. The background noise samples were acquired from a laboratory room using a software-defined radio platform NI USRP-2900. The reasonability of the proposed detection approach is confirmed by the results achieved in the modeled system.