The low frequency voltage noise and complex AC voltage response to weakly modulated magnetic fields have been studied in a superconducting Pb film with a square lattice of antidots. The temperature was close to T_c and the DC magnetic field was changed between ±1.5 H₁ with H₁=9.2 Oe corresponding to one vortex per antidot. A narrow band noise near f≈0.55 Hz has been observed which shows different dependences on the magnetic field in 4- and 5-point probe configurations. In the latter configuration one probes the correlation between the noise voltages in the two parts of the sample. We also measured the resistance when, in addition to the DC field, a small AC field with frequency f<177 Hz was applied. The data showed that the complex magnetoresistance response becomes nonlinear below 1/3 of the first matching field.