Figure 1: The aluminum screen material in the configuration used for this experiment was tested at NIST in Boulder, CO. From 1.0 MHz to 3.0 GHz, its effectiveness in blocking RF signals was found to vary from 40 dB to 73 dB across the entire range of frequencies. axis = Radio frequency from 1.000 MHz to 3000.000 MHZ in increments of 300.000 MHz left to right. axis = Decibel scale. Reference signal level was 90 dB. A = Reference signal. B = Attenuated signal.