# Influence of the Nasometric Instrument Structure on Nasalance Score
## 3 Nasalance Characteristics according to the Structure of the Nasometric Instrument
### Experimental Results
In the case of female mean nasalance, it was also measured as low as 3% to 15%. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Healthy Control Group**} & \multicolumn{2}{c}{**/a/**} & \multicolumn{2}{c}{**/mama/**} & \multicolumn{2}{c}{**/mimi/**} \\ \cline{2-9}  & \multicolumn{2}{c}{**Nasalance**} & \multirow{2}{*}{**Corr.**} & \multicolumn{2}{c}{**Nasalance**} & \multirow{2}{*}{**Corr.**} & \multicolumn{2}{c}{**Nasalance**} & \multirow{2}{*}{**Corr.**} \\  & & **[\%]** & & & & **[\%]** & & \\ \hline \multirow{9}{*}{Using the separation structure} & Male1 & 19.73 & 0.4299 & 40.40 & 0.3530 & 66.45 & 0.7659 \\  & Male2 & 17.81 & 0.2532 & 31.47 & 0.3825 & 56.15 & 0.6702 \\  & Male3 & 16.38 & 0.2687 & 34.62 & 0.3634 & 62.24 & 0.6292 \\  & Female1 & 18.09 & 0.2624 & 43.26 & 0.2272 & 79.94 & 0.7645 \\  & Female2 & 7.74 & 0.1927 & 40.80 & 0.2379 & 68.67 & 0.8664 \\  & Female3 & 20.18 & 0.3024 & 35.27 & 0.3724 & 69.22 & 0.7655 \\ \hline \multirow{9}{*}{Using the mask structure} & Male1 & 19.78 & 0.7725 & 32.22 & 0.4669 & 51.73 & 0.5594 \\  & Male2 & 14.65 & 0.7760 & 40.63 & 0.5030 & 61.83 & 0.7622 \\ \cline{1-1}  & Male3 & 13.08 & 0.6640 & 30.62 & 0.5680 & 53.19 & 0.5639 \\ \cline{1-1}  & Female1 & 17.99 & 0.5990 & 32.19 & 0.4490 & 68.02 & 0.7886 \\ \cline{1-1}  & Female2 & 10.54 & 0.4675 & 32.50 & 0.3755 & 60.57 & 0.8097 \\ \cline{1-1}  & Female3 & 12.42 & 0.7451 & 30.15 & 0.5369 & 57.28 & 0.8772 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Correlation coefficients and nasalance results of the healthy control group. Figure 9: Measured spectrum of vocal signal of females using the separation-type structure for (**a**) /a/, (**b**) /mama/, and (**c**) /mimi/, and measured spectrum of vocal signal of females using the mask-type structure for (**d**) /a/, (**e**)/mama/, and (**f**)/mimi/ (the red line is the microphone output in the oral direction and the blue line is the microphone output in the nasal direction). In the case of the male mean correlation coefficient between oral and nasal speech signals, the mask type was found to be about 0.20 to 0.45 (/a/,/mama/) higher than that of the separation plate type. In the case of /mimi/ words, the result was slightly higher (0.01). The average correlation coefficient of the female was also found to be about 0.2 to 0.38 for /a/ and /mama/ sounds;/mimi/ words showed results about 0.02 higher. Referring to Figure 10, as the correlation coefficient increases, the nasalance tends to decrease, which means that the nasalance is lower as the signals of the oral and nasal sounds are similar. The design of the mask-type nasometric instrument to minimize the influence of acoustic feedback is less affected by the interference than the nasometric instrument of the separator type and exhibits a relatively high correlation between the oral and nasal signals. The higher the correlation, the lower the nasalance of the healthy control group. The mask-type nasometric instrument results are about 5% to 15% lower than the separator-type nasometric instrument results. This is because the mask structure, based on the low-pass filter, suppresses frequency components above about 500 Hz of the measured speech signal, and it is relatively similar to the nasal signal component in the low-frequency band.