**3.1 Influence of speech intelligibility on brainwaves**

Monosyllabic speech sounds had a major effect on both α-waves (*F* = 12.96 (9, 2488), *p* < 0.001) and β-waves (*F*(9, 2488) = 5.21, *p* < 0.001) at different first reflection delay times. As shown in **Figures 6** and **7**, the ACF of β-waves recorded in the left hemisphere was positively correlated with subjective perceptions of speech intelligibility. With regard to α-waves in the left hemisphere, brainwave

**43**

**Figure 7.**

*Relationship between τe of ACF, β-wave and Δt1 of sound field.*

*The Influence on Cortical Brainwaves in Relation to Word Intelligibility and ASW in Room*

responses tended to increase at 100 ms for all sounds apart from "tzuen1." It is not clear whether these results were related to the nasal sounds "uen." The psychological experiment results (**Figure 2**) showed that the lowest articulation rates were observed for four sounds at 100 ms reflection delays. An opposite tendency was

*DOI: http://dx.doi.org/10.5772/intechopen.85044*

**Figure 6.** *Relationship between τe of ACF, α-wave and Δt1 of sound field.*

*The Influence on Cortical Brainwaves in Relation to Word Intelligibility and ASW in Room DOI: http://dx.doi.org/10.5772/intechopen.85044*

responses tended to increase at 100 ms for all sounds apart from "tzuen1." It is not clear whether these results were related to the nasal sounds "uen." The psychological experiment results (**Figure 2**) showed that the lowest articulation rates were observed for four sounds at 100 ms reflection delays. An opposite tendency was

**Figure 7.** *Relationship between τe of ACF, β-wave and Δt1 of sound field.*

*The Human Auditory System - Basic Features and Updates on Audiological Diagnosis and Therapy*

Monosyllabic speech sounds had a major effect on both α-waves (*F* = 12.96 (9, 2488), *p* < 0.001) and β-waves (*F*(9, 2488) = 5.21, *p* < 0.001) at different first reflection delay times. As shown in **Figures 6** and **7**, the ACF of β-waves recorded in the left hemisphere was positively correlated with subjective perceptions of speech intelligibility. With regard to α-waves in the left hemisphere, brainwave

**3. Empirical results and discussion**

**3.1 Influence of speech intelligibility on brainwaves**

**42**

**Figure 6.**

*Relationship between τe of ACF, α-wave and Δt1 of sound field.*

detected in the articulation rate results related to "yu2," "he4," and "ian1." The 100 ms delay is close to the 135 ms slow response delay proposed in Ando's [22] study on sound field preferences (echo disturbance). The displeased response of α-waves to the delay time of reflection [14] requires further investigation.

**Figure 7** shows changes in β-waves. Consistent results were obtained with regard to the influence of the delay time of reflection on the left hemisphere (*F*(9, 2488) = 5.21, *p* < 0.001). However, no significant differences were observed in psychological reactions to speech intelligibility. A significant relation between articulation rates and the order of reactions was detected in the mean values related to the right hemisphere. Thus, left hemisphere showed changes in β-waves in relation to the order of delay time on reflection but speech intelligibility reactions.

## **3.2 Changes in subjective perception of ASW and brainwaves**

The findings related to SVR to evoked potentials of nine participants are shown in **Figure 8**. With regard to the left hemisphere, SVR relative amplitude were consistently and inversely related to quantified psychological scale values (*F*(1, 16) = 4.90, *p* < 0.05). However, clear results were difficult to obtain due to the small difference between ASW (−0.16) and ASW (0.03).

Latency changes in the left and right hemispheres indicated the presence of a significant difference between ASW (0.03) and ASW (0.45) only at N2 in the left hemisphere (*F*(1, 16) = 11.09, *p* < 0.05). The tendency of ASW (0.45) latency being smaller than ASW (0.03) latency in the left hemisphere can be seen from **Figure 9**, whereas in the right hemisphere, ASW (0.45) latency was consistently

**45**

in **Figure 3**.

**Figure 9.**

**4. Conclusions**

*The Influence on Cortical Brainwaves in Relation to Word Intelligibility and ASW in Room*

larger than ASW (0.03) latency. The results showed that relative amplitude in the left hemisphere were caused by subjective perceptions of ASW, which influenced the participants' preference toward a sound field. The consistency of latency at N2 was due to the activation of neural sites, which was clearly observed between ASW (0.03) and ASW (0.45), as well as at IACCE3 of 0.56–0.68. Thus, the brain did not have a major effect on the corresponding changes at the extreme IACCE3 values of 0.35 and 0.81, which corresponded to the psychological reaction results presented

The arrangements and results of the aforementioned brainwave experiments indicated that when simple physical changes in a sound field and complex psychological feedbacks affect cerebral brainwave reactions, the correspondence of the cerebral specialization theory with the results becomes very complicated. In general, in this study, the left hemisphere tended to be activated in both temporal and spatial aspects based on the sound field. When the participants' brainwaves were recorded during the judgment task, the brain activation in the right hemisphere tended to reflect the discriminated object more closely. When CBW were observed during research on speech intelligibility, the left hemisphere showed clear reactions to the first reflection delay time of sound field (**Figure 7**). However, the degree of speech intelligibility is a reflection of the complex thinking process that occurs in the right hemisphere (cerebral feedback). This phenomenon was supported by the subjective ASW experiment. With regard to changes in spatial factors, the left hemisphere received information

*DOI: http://dx.doi.org/10.5772/intechopen.85044*

*Relationship between latency, SVR and ASW of sound field.*

**Figure 8.** *Relationship between potential, SVR and ASW of sound field.*

*The Influence on Cortical Brainwaves in Relation to Word Intelligibility and ASW in Room DOI: http://dx.doi.org/10.5772/intechopen.85044*

**Figure 9.** *Relationship between latency, SVR and ASW of sound field.*

larger than ASW (0.03) latency. The results showed that relative amplitude in the left hemisphere were caused by subjective perceptions of ASW, which influenced the participants' preference toward a sound field. The consistency of latency at N2 was due to the activation of neural sites, which was clearly observed between ASW (0.03) and ASW (0.45), as well as at IACCE3 of 0.56–0.68. Thus, the brain did not have a major effect on the corresponding changes at the extreme IACCE3 values of 0.35 and 0.81, which corresponded to the psychological reaction results presented in **Figure 3**.
