Spectrum sensing is a feature of cognitive radio systems which is proposed to improve spectral utilization of wireless signals. One of the sensing method is the noncoherent energy detector, and even though it is computationally more effective than coherent methods such as matched filtering, it has critical drawbacks e.g., requirement of certain signal to noise ratio and number of samples. Moreover, type of digital modulation employed also affects the performance of the energy detectors. Therefore, in this paper, the performance of the energy detectors are investigated for phase shift keying and quadrature amplitude modulated signals. Instead of false alarm and missed detection analysis, probability mass function vs. energy detection statistics are introduced to better understand the effect of modulation type, order and wireless channel. A measurement setup is developed also considering line of sight and non-line of sight conditions and signals are constructed, transmitted and recorded based on the signal model provided. The measurement results indicate that modulation type and order have significant impact on detection statistics.