The same experiment was repeated with the transducer placed on the anode of the electrolyser, these results are shown in Figure In order to compare the acoustic activity at the anode and cathode at all current densities studied, the hit rate (number of hits per second) was calculated for all areal current values on both electrodes, the data from these calculations are shown in Figure range there is an increase in the rate of increase of acoustic hits per second with increasing current density, suggesting more bubble formation; this is a similar trend to that observed with the voltage fluctuation experiments. This increase in acoustic activity is observed with both the anode and the cathode. At current densities above ca.. 75 mA cm - the hit rate for the cathode is always higher than that observed at the anode, indicating more prevalent bubble formation at the cathode. At higher current densities, above the 200-300 mA cm -2 range, this difference in acoustic activity increases further with a higher gradient observed with the cathode relative to the anode (Figure (a)). This again matches well with results obtained from voltage fluctuation experiments. This difference between the higher acoustic activity observed with the cathode relative to the anode, particularly at current densities above 200-300 mA cm -2 is more clearly observed by studying the cumulative energy of the acoustic hits (Figure (b)). Thus far, the focus has been on the number of hits recorded, which gives a good indication of the acoustic activity but does not include all information. By looking at the cumulative energy, this not only takes into account the total number of hits but other factors associated with each hit such as the duration and frequency of each hit. Based on the cumulative energy the performance of the two electrodes is relatively similar, albeit with the cathode showing slightly higher energy, until approximately 1500 s. At this point, where the current density is increased beyond 200 mA cm - prevalent at the cathode and for higher current densities above ca. 200 mA cm -2 the effect is initially larger on the cathode than the anode.