## 3 Results and Discussion
### Discharge of Inert Gases: Effect of Generated Noise
According to Dutta [31], noise can affect hard drive performance even beyond a 105 dB threshold at a frequency between 4 and 10 kHz. Figure 7: SPL and disk performance index as a function of time throughout a nitrogen IG100 discharge by (**a**) standard and (**b**) silent nozzle with 5 mm orifice diameter; (**c**) standard and (**d**) silent nozzle with 10 mm orifice diameter; (**e**) standard and (**f**) silent nozzle with 14 mm orifice diameter; (**g**) standard and (**h**) silent nozzle with 17 mm orifice diameter; (**i**) standard and (**j**) silent nozzle with 23 mm orifice diameter. When comparing hard drive performance, the difference between configurations with the standard nozzle and those with the silent ones is highlighted by HDD performance index trends. As expected, solid-state storage devices (i.e., SDD) are almost not affected by external noise, hence SDD performance was close to 100% throughout each conducted experiment (Figure 7). The exhibited mild oscillations--in some instances even leading to performance higher than the nominal one (i.e., greater than 100%)--appear unrelated to the actual experimental conditions. On the other hand, HDD performance decay is highly consistent with SPL exceeding the 110 dB threshold; moreover, the higher the SPL, the greater the performance decay (Figure 7). This observation is particularly emphasized by HDD1, which is the hard drive featuring the smaller rate of rotation, and consequently, the lower nominal speed (Table 2); HDD2 seemed less affected by noise, to the point of having its performance almost unaffected by SPL lower than 120 dB and also by noise regrowth for a short timespan (Figure 7c,g). It is also worth noting that HDD1 did not recover its performance level under undisturbed conditions as noise fell below the threshold, due to the discharge by the standard nozzle approaching the end of the process (Figure 7c,g,i); this phenomenon never appeared in tests run with silent nozzles instead. This prolonged performance loss occurring with the discharge produced by standard nozzles with large orifice diameters is arguably due to SPL being above 100 dB at frequencies greater than  
Figure 8: SPL as a function of time and OTO (One-Third Octave bands) frequency throughout a nitrogen IG100 discharge by (**a**) standard and (**b**) silent nozzle with 10 mm orifice diameter; (**c**) standard and (**d**) silent nozzle with 17 mm orifice diameter; (**e**) standard and (**f**) silent nozzle with 23 mm orifice diameter. 4 kHz over a wide portion of the discharge event (Figure 8a,c,e). As previously reported, Dutta suggests that hard drives are affected by SPLs as low as 105 dB in the 4-10 kHz band [31], which may explain the result of only partial recovery even when noise fell below 110 dB. The diagram of Figure 9 serves as an overview of the impact of noise from the tested nozzles on hard drives: (maximum) performance loss is plotted against maximum SPL reached for each tested condition, including both standard and silent nozzle experiments. An apparent correlation between HDD read/write speed and noise appears from the performance dataset, with HDD performance becoming lower as SPL increases. The linear best-fitting curve, applied to each database related to the three tested hard drives, emphasizes that noise is more impactful against the HDD featuring lower nominal speed with respect to those with higher rates of rotation.