## 3 Results  
Figure 3 shows a comparison of the two transducers. The shapes of the CT-based transducer were not always identical to those of the impression-based transducer. However, both transducers were worn smoothly without any serious problems. Although the slice width of CT ranged from 0.4 to 1.0 mm (Table 1), the surfaces of the transducers were not especially rough, and the quality of their shape was acceptable for use in daily life. Table 1 lists the mass of the transducers. In most cases, the mass of the CT-based transducer was slightly larger than that of the impression-based transducer.  
Figure 4 shows the thresholds aided by the hearing aids. No significant differences were observed between the two transducers. After the trial in daily life, there was no obvious difference in subjective hearing. The assessment of hearing after wearing hearing aids was performed according to the Japanese guidelines for the evaluation of hearing aid fitting [23]. As no remarkable differences in subjective hearing were observed between both transducers, the assessment using 10 questionnaires mentioned in the guidelines was performed for CC hearing devices together, not separately between two transducers. The assessments were judged to be sufficient. Table 2 shows the subjective patient preference after the 2-4-week trial. Comparing both devices, although hearing was subjectively better with the CT-based transducer in Patient 1, the stability of the CT-based transducer in  
Figure 3: Transducers designed via ear impression (**left**) and CT images (**right**). CT, computed tomography.  
the right ear was inferior, and wearing comfort was better with the impression-designed transducer in the left ear. After the trial, Patient 1 chose the transducer designed based on ear impression for the hearing aids. Subjective hearing was also better with the CT-based transducer in Patient 2. However, wearing comfort and appearance were inferior to those of the impression-based transducer. Patient 2 also chose the impression-designed transducer for the hearing aid. In contrast, in Patient 3, no difference in the subjective patient hearing and wearing comfort was observed between the two transducers. However, the mass of the CT-based transducer was smaller. Patient 3 chose the CT-based transducer because of its better appearance.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Patient** & **Ear** & **Hearing** & **Wearing Comfort** & **Appearance** & **Purchased** \\ \hline \multirow{2}{*}{1} & Left & CT images & Impression & No difference & Impression \\ \cline{2-6}  & Right & CT images & Impression & No difference & Impression \\ \hline
2 & Right & No difference & No difference & CT images & CT images \\ \hline
3 & Left & CT images & Impression & Impression & Impression \\ \hline \hline \end{tabular} This table shows preferred transducer in terms of hearing, comfort when worn, and appearance. It also shows which transducer was purchased after trial. CT, computed tomography.  
\end{table}
Table 2: Subjective patient preference in each category and transducer purchased after trial.  
Figure 4: Aided thresholds. CT, computed tomography.  
Summarizing the results, the CT-based transducer provided subjectively better hearing in three ears, whereas no difference was found in the aided thresholds between the two devices. Wearing comfort was better with the impression-based transducers. The subjective appearance varied among the patients. Finally, the CT-based transducer was chosen by one of the three patients.