How to Measure the Effectiveness of Absorbers for SMPS (Switching Mode Power Supply)

How to measure the effectiveness of absorbers placed next to a low frequency switching power supply (SMPS).
Model: EMxpert ERX+
DUT: The device tested in this video is an evaluation board for high efficiency, small footprint step-down DC-DC converter. This is an off-the-shelf commercial product that just pulled the board out.
Spectrum Analyzer: ERX+ is a plug 'n play system. It has an embedded spectrum analyzer.