## 4 Experiment
### Results  
Table 1 shows the EERs on the trials of both development and evaluation sets according to the methods for handling variable length sequences without self-attention. On average, _max/bmax_ showed relatively lower EERs of about 9.2% than _mean/bmean_. This means that the loss of information from truncation is worse than the addition of unnecessary information from padding. On the other hand, against our expectation, there was no consistent trend with the other conditions. For example, _const_ did not always show higher EERs than _ret_. Also, _front_ did not always show lower EERs than _end_, unlike in [23]. Notice that both speaker information and phrase information are important in TD-SV. In general, _const_ can maintain the identity of phrase, although the discriminative power between speakers can be degraded. Whereas, _ret_ can maintain speaker information, although the identity of phrase is somewhat changed. It can be seen that there is a trade-off between _const_ and _ret_, while there is no significant difference between _front_ and _end_ in TD-SV. Except on the female evaluation trials, the proposed method showed the lowest EERs, exhibiting relative reductions of approximately from 1.3% (i.e., compared with PackedSequence) to 27.1% (i.e., compared with _bmean_front_rept_) in the development trials, and from 3.8% (i.e., compared with PackedSequence) to 20.8% (i.e., compared with _mean_front_rept_) on the male evaluation trials. These results correspond with our expectations that reducing the information distortion can improve performance, and it is shown that the proposed method can remove information distortion. On the female evaluation trials, the _max_end_rept_ showed the lowest EER. The proposed method showed the second lowest EER, but only relatively about 0.2% higher than the _max_end_rept_. Therefore, it is difficult to say that there is a significant difference between them. Table 2 shows the EERs with self-attention. Attention emphasizes more important frames by applying different weights. As in Table 1, _max/bmax_ still show relatively lower EERs of approximately  
7.6% than _mean/bmean_ in general. Even so, the gap between the EERs was slightly decreased, relatively about from 9.2% to 7.6%. This means that attention can compensate for information loss somewhat. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Method**} & \multirow{2}{*}{**Development**} & \multicolumn{2}{c}{**Evaluation**} \\ \cline{3-4}  & & **Male** & **Female** \\ \hline _max\_front\_const_ & 5.9814 & 5.4696 & 5.7919 \\ _max\_front\_rept_ & **5.0286** & 4.7755 & 5.2656 \\ _max\_end\_const_ & 6.0851 & 5.2865 & 5.9126 \\ _max\_end\_rpt_ & 5.1067 & 4.7189 & 5.2431 \\ \hline _mean\_front\_const_ & 6.2526 & 5.5981 & 5.7569 \\ _mean\_front\_rept_ & 6.0607 & 5.5753 & 5.9489 \\ _mean\_end\_const_ & 5.8732 & 5.1386 & 5.8918 \\ _mean\_end\_rpt_ & 5.9291 & 5.3014 & 5.8448 \\ \hline _bmax\_front\_const_ & 6.148 & 5.235 & 5.1985 \\ _bmax\_front\_rept_ & 5.3502 & 4.5813 & 5.2674 \\ _bmax\_end\_const_ & 6.4357 & 5.2748 & 5.4604 \\ _bmax\_end\_rpt_ & 5.2754 & 5.002 & 5.4826 \\ \hline _bmean\_front\_const_ & 6.3489 & 5.4201 & 5.7655 \\ _bmean\_front\_rept_ & 6.515 & 5.4798 & 6.266 \\ _bmean\_end\_const_ & 6.1184 & 5.3527 & 5.6719 \\ _bmean\_end\_rpt_ & 6.0218 & 5.6071 & 6.3661 \\ \hline \multicolumn{2}{c}{PackedSequence} & 5.3949 & 4.6406 & 5.2572 \\ \hline \multicolumn{2}{c}{Proposed} & 5.1206 & **4.2291** & **5.039** \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The EERs (%) of systems without self-attention on the development and evaluation trials of RSR 2015 part 2. The lowest EERs among all the methods are highlighted in bold, the lowest EERs among all the methods except the proposed method are underlined.