A system for measuring the attenuation of electromagnetic shielding of an infrastructure as a function of the frequency, including a transmitter of a white noise signal with a constant power over a frequency band between a minimum frequency and a maximum frequency, a signal receiver, the transmitter and the receiver being capable of sending a signal and receiving a signal across the infrastructure, the receiver including a filter module capable of applying sliding filter on the received signal between the minimum frequency and the maximum frequency, and a double synchronous detection module capable of double synchronous detection on a signal output by the filter module.