# Reading Tapes Backwards: A Legitimate Approach to Saving Time and Money in Digitization Projects?
## 4 Results and Discussion
The biggest differences are shown in complex signals, that is, they are less constant in time and have a wide band spectrum. For instance, the average value increases more for the drum, song and white noise with respect to the train of impulses or the sweep. The average values are shown in Table 2 together with the ratio between the two values for the congruent and non-congruent readings of the same block. The ANOVA performed on the new dataset highlighted the correlation between NED and the congruent and non-congruent recordings, as shown in Table 3.  
A Welch two samples \(t\)-test was performed between the two types of comparisons within the same block. The results show that the distributions are not the same and highlight the non-negligible difference between them (see Table 2). Furthermore, the analysis of NED differences between congruent forward readings and congruent backward readings shows that the distributions have non-negligible differences, and for all the blocks the resulting \(p\)-value is always <0.001 (see Table 4), even if the average values have a lower ratio with respect to the forward and backward readings. These results suggest that, according to the NED parameter, opposite readings do not ensure the same results and may provide non-negligible differences in the audio file. Furthermore, even if the analog process of recording does not provide constant results, multiple forward readings can be compared to multiple backward readings, since the results are not the same but can be easily compared. \begin{table}
\begin{tabular}{c c} \hline \hline
**Number of Frames** & \(p\)**-Value** \\ \hline
233 & \(<\)0.001 \\
100 & 0.08 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: ANOVA \(p\)-values between NED and frames; 233 frames show a correlation between the two parameters. Vice versa, 100 frames show no correlation. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Audio** & **AVG Cong.** & **AVG Non-Cong.** & **Ratio** & \(p\)**-Value** \\ \hline Classical & 0.54 & 7.03 & 13.01 & \textless{}0.001 \\ Drum & 2.27 & 7.61 & 3.14 & \textless{}0.001 \\ Impulses & 2.24 & 2.53 & 1.12 & \textless{}0.001 \\ Song & 0.09 & 7.11 & 79 & \textless{}0.001 \\ Speech & 0.10 & 3.66 & 36.6 & \textless{}0.001 \\ Sweep & 2.38 & 4.01 & 1.68 & \textless{}0.001 \\ White & 12.10 & 15.21 & 1.25 & \textless{}0.001 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: AVG Cong. shows the average NED for congruent comparisons; AVG Non-Cong. shows the average NED for non-congruent comparisons; Ratio shows the ratio between congruent AVG and non-congruent AVG; \(p\)-value refers to a Welch Two Samples \(t\)-test between congruent and non congruent NEDs of the same block. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & \(p\)**-Value** \\ \hline Congruent & \(<\)0.001 \\ Non-congruent & \(<\)0.001 \\ Block & \(<\)0.001 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: ANOVA \(p\)-values between NED and Congruent, Non-Congruent and Block. Audio production and preservation are two important areas in the non-academic world, audio being a huge driver in the creative economy around the globe. Especially in the past decades, practices that have been shared among the _expert community_ have not been formalized in the scientific literature. As a result, much knowledge and useful information, relevant to academic studies including the present one, are in the heads of audio veterans \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Audio** & **Forward** & **Backward** & _p-Value_ \\ \hline Classical & 0.95 & 0.13 & \textless{}0.001 \\ Drum & 2.46 & 2.08 & \textless{}0.001 \\ Impulses & 2.32 & 2.16 & \textless{}0.001 \\ Song & 0.46 & \textless{}0.66 & \textless{}0.001 \\ Speech & 0.46 & \textless{}0.25 & \textless{}0.001 \\ Sweep & 2.59 & 2.17 & \textless{}0.001 \\ White & 11.14 & 10.95 & \textless{}0.001 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Averages and _p-_values resulting from the t-test performed on the blocks of forward and backward readings.