**2. Empirical methods**

### **2.1 Psychological test of intelligibility**

This study used monosyllabic speech sound articulation and IACCE3 to quantify changes in two subjective experiences, namely, speech intelligibility and ASW. With regard to speech intelligibility, the fifth group of common Chinese monosyllabic speech sounds used in Taiwan [8] (female voice, **Table 1**) was used. Test results related to this group of monosyllabic sounds are characterized by the largest disparity in error rates because most related sounds belong to "fricative sounds" (i.e., apical vowels, such as "zh," "ch," "sh," "r," "z," "ci," and "si" in Bopomofo system). The amounts of fricative and non- fricative rhymes are balance (eight versus ten, respectively).

**37**

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

**Chinese monosyllable** shy0 7 yu2 13 ching3 iur1 8 leau3 14 tzuen1 li0 9 shoou3 15 cha2 meei3 10 ian1 16 shuo4 tsae3 11 tsong1 17 he4 ru2 12 guang1 18 chye2 *Note: The pronunciation of each syllable depends on the tone (one of five pitch contours) used, which is indicated by a number attached to the end of the syllable. For example, 0 denotes monosyllables pronounced with a soft puff of air.*

The sound structure of Mandarin differs from that of other languages. In Mandarin, each character is pronounced as a monosyllable with one of five tones (i.e., types of pitch contour). Each of these tones (0–4), when used with a given monosyllable, causes the monosyllable to convey a meaning distinct from those conveyed when the monosyllable is used with the other four tones. Utterance lengths in the experiment were set to 400–500 ms. Monosyllabic presents were separated by 2.5 s. The experiment was arranged according to the arrangement used in the study by Chen et al. [9]. The experiment was conducted in front of two overlapping loudspeakers in a semianechoic room (4 × 3 and 4 m in height) at Chaoyang University of Technology. The loudspeakers (Fostex NF-1A) were located at 1.5 m right front of the center of a listener's head. The first reflected sound was given off by the upper loudspeaker (*η* = 15) while another gave off the direct sound (*η* = 0). To vary speech intelligibility, the speech signal was assumed that emitted from the stage with a direct and a reflection sound reflected through the ceiling of the stage. The listening level was adjusted to a usual communicative sound volume of 62 dB(A) at the center of the room. The level of background noise in the semi-anechoic room was 32–42 dB(A), then the S/N ratio are approximate to 30–40 dB. The setup of the instrumental diagram (EEG recordings) could be referred to **Figure 1**, since they were same as that in the spatial ASW experiment stated below. The settings of the physical parameters used in the experiment are shown in **Table 2**. **Figure 2** shows the experimental results that indicate 62 listeners who were significantly able to distinguish sounds using percentage syllable articulation (PSA) tests [10]. To determine PSA, those written syllables are compared

with the original syllables to find the percentage of syllables written correctly.

The paired-comparison method [11] was used in the psychological quantification test of subjective ASW. The experiment was conducted in the same venue as the first experiment. Three loudspeakers (one for direct sounds and two for reflected sounds) were located at 1.5 m from the center of a listener's head; the incidence combinations (**ξ, η**) are: (0°, ±15°), (0°, ±55°), (0°, ±90°) and (0°, +15°, −55°) on the horizontal plane. 2 kHz pure-tone (1 ms) sounds were produced. The IACCE3 (0.35, 0.57, 0.68, and 0.81) [12, 13] of the sound field was changed by changing the angle of incidence stated above and the sound pressure level. As a result, different subjective ASWs were generated (**Table 3**). The instrumental setup of testing spatial ASW and the process of AEPs recordings are interpreted in **Figure 1**. The participants (80 students) determined ASWs using paired comparisons. The interval between sound prompts within one group was 2 s and the interval between groups was 10 s; in total, six groups were used. The participants were asked to

**2.2 Psychological quantification test of ASW**

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

**Table 1.**

*List of the term of monosyllables [8].*

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


*Note: The pronunciation of each syllable depends on the tone (one of five pitch contours) used, which is indicated by a number attached to the end of the syllable. For example, 0 denotes monosyllables pronounced with a soft puff of air.*

#### **Table 1.**

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

design belong to non-speech functions. For instance, the range of non-speech functions includes aesthetic perception and the feeling of balance. In particular, many non-speech symbols can be observed in environmental design. Earlier research on audio and cerebral correlations found that such common medical problems as aphasia and disturbances in tone judgment originate in the left cerebral hemisphere. Therefore, this study suggested that cerebral responses to speech and non-speech symbol in the physical environment effectively substitute for the semantic differences (SD) caused by age-related and cultural differences. Cerebral responses to communication stimuli are a direct cross-cultural and cross-age reference indicator, which is similar to the principle behind polygraph tests performed by police to

This study suggested that cerebral responses can be used to clearly and consistently examine responses to change in "speech functions" of the physical environment, or speech intelligibility, when designing a sound field. Ando [2] considered "speech functions" to be an important temporal factor and the result of autocorrelation function (ACF) evaluations in the brain. Therefore, the environmental effects of temporal factors were examined in this study based on the influence of speech intelligibility on the correlation between "subjective perceptions" and cerebral responses, which served as the basis for the objective design of an acoustic environment. Akita et al. [5] indicated that when the sensory information received by listeners is analyzed by brainwaves, this does not represent their direct experience of changes in the environment, but rather the interaction between physiology and the environment. This phenomenon is common in daily life. The intensity of cerebral evoked responses is the optimal evaluation tool [6]. Soeta et al. [7] studied the effects of sound source features on subjective psychological responses and cerebral responses measured by magnetoencephalography (MEG) and reported that at different delay times of reflection sounds (Δ*t*1 = 0, 5, 20, 60, and 100 ms) and 50 alternations, the ACF effective delay time of α-waves recorded by MEG indicated subjective preferences regarding sound fields. The methods used in this study can

1.The first reflection delay (Δ*t*1) was changed to change speech intelligibility. The degrees (or process) of subjective recognition of Chinese monosyllables were determined by comparing ACF calculation results related to α-waves and

2.The IACCE3 was changed to change subjective ASW. Changes in the waveforms of auditory evoked potentials (AEPs) during listeners' perceptions of spatial

This study used monosyllabic speech sound articulation and IACCE3 to quantify changes in two subjective experiences, namely, speech intelligibility and ASW. With regard to speech intelligibility, the fifth group of common Chinese monosyllabic speech sounds used in Taiwan [8] (female voice, **Table 1**) was used. Test results related to this group of monosyllabic sounds are characterized by the largest disparity in error rates because most related sounds belong to "fricative sounds" (i.e., apical vowels, such as "zh," "ch," "sh," "r," "z," "ci," and "si" in Bopomofo system). The amounts of fricative and non- fricative rhymes are balance (eight versus ten, respectively).

β-waves among cerebral continuous brainwaves (CBW).

examine physiological responses.

be summarized as follows:

ASW were analyzed.

**2.1 Psychological test of intelligibility**

**2. Empirical methods**

**36**

*List of the term of monosyllables [8].*

The sound structure of Mandarin differs from that of other languages. In Mandarin, each character is pronounced as a monosyllable with one of five tones (i.e., types of pitch contour). Each of these tones (0–4), when used with a given monosyllable, causes the monosyllable to convey a meaning distinct from those conveyed when the monosyllable is used with the other four tones. Utterance lengths in the experiment were set to 400–500 ms. Monosyllabic presents were separated by 2.5 s. The experiment was arranged according to the arrangement used in the study by Chen et al. [9].

The experiment was conducted in front of two overlapping loudspeakers in a semianechoic room (4 × 3 and 4 m in height) at Chaoyang University of Technology. The loudspeakers (Fostex NF-1A) were located at 1.5 m right front of the center of a listener's head. The first reflected sound was given off by the upper loudspeaker (*η* = 15) while another gave off the direct sound (*η* = 0). To vary speech intelligibility, the speech signal was assumed that emitted from the stage with a direct and a reflection sound reflected through the ceiling of the stage. The listening level was adjusted to a usual communicative sound volume of 62 dB(A) at the center of the room. The level of background noise in the semi-anechoic room was 32–42 dB(A), then the S/N ratio are approximate to 30–40 dB. The setup of the instrumental diagram (EEG recordings) could be referred to **Figure 1**, since they were same as that in the spatial ASW experiment stated below. The settings of the physical parameters used in the experiment are shown in **Table 2**. **Figure 2** shows the experimental results that indicate 62 listeners who were significantly able to distinguish sounds using percentage syllable articulation (PSA) tests [10]. To determine PSA, those written syllables are compared with the original syllables to find the percentage of syllables written correctly.

#### **2.2 Psychological quantification test of ASW**

The paired-comparison method [11] was used in the psychological quantification test of subjective ASW. The experiment was conducted in the same venue as the first experiment. Three loudspeakers (one for direct sounds and two for reflected sounds) were located at 1.5 m from the center of a listener's head; the incidence combinations (**ξ, η**) are: (0°, ±15°), (0°, ±55°), (0°, ±90°) and (0°, +15°, −55°) on the horizontal plane. 2 kHz pure-tone (1 ms) sounds were produced. The IACCE3 (0.35, 0.57, 0.68, and 0.81) [12, 13] of the sound field was changed by changing the angle of incidence stated above and the sound pressure level. As a result, different subjective ASWs were generated (**Table 3**). The instrumental setup of testing spatial ASW and the process of AEPs recordings are interpreted in **Figure 1**. The participants (80 students) determined ASWs using paired comparisons. The interval between sound prompts within one group was 2 s and the interval between groups was 10 s; in total, six groups were used. The participants were asked to

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

#### **Figure 1.**

*The setup of the instrumental diagram (audio arrangement and EEG recordings).*


#### **Table 2.**

*The setting of the physical parameters in subjective articulation test of monosyllables.*

immediately determine and record the relative probability of ASWs. Each questionnaire was conducted for 1 min. The psychological scale values of ASWs are shown in **Figure 3** calculated using Thurstone's Case V [11]. Non-linear correlation was observed in the IACCE3 result [14].

### **2.3 Brainwave physiological experiment methods**
