We report the results of low frequency voltage noise measurements on very small area (A = 0.05 to 1 μm2) Nb-Nb2O5-PbBi tunnel junctions as a function of tunnel junction quality and over a wide range of voltage and temperature. We find that the noise spectrum Svin our bandwidth (1Hz to 25.6kHz) is largely composed of a small number (2-3) of distinct Lorentzian components each of which can be characterized by its own voltage and temperature dependent magnitude and mean rate. These lorentzian components provide a powerful means to probe the actual microscopic fluctuation events which lead to 1/f noise in larger devices. The ensemble average spectrum of our devices trends about a 1/f frequency dependence and has a magnitude proportional to (IRj)2and 1/A. We have used our results to establish the intrinsic low frequency energy sensitivity of d.c. SQUIDs made with shunted tunnel junctions.