  We study the effect of an AC bias on the low frequency noise, notably
$1/f^\gamma$ with $\gamma<2$, of metal-insulator-metal tunnel junctions at room
temperature. The measurement is performed in the 6Hz-100kHz frequency range
with an AC excitation above 1MHz. We observe that $1/f^\gamma$ noise is
dominant across our measurements though the shape of the spectra varies. The
effect of the DC excitation seems to be very different on the noise generated
by the junction than that of the AC excitation, thus questioning the fact that
the observed noise is due to resistance fluctuations that the bias only
reveals.
