**4. Ability to guide evacuees by emitting sound along predetermined paths**

### **4.1 Experimental condition of experiment 3**

We conducted the third experiment to investigate whether the subjects were able to follow the sound emitted along the evacuation paths. Additionally, we investigated whether it is possible for people to follow complex routes that have a lot of turning points on it. In this experiment, the complexity of the guidance is defined by the number of turning points on itself. As the number of turning points included in a guidance patten increases, it gets more complicated. In case of moving along the more complex path on which subjects turn to the right and left repeatedly in a short time, more accurate and quick sound localization is required to identify the sound stream. Therefore, we defined the complexity of the evacuation path by the number of turning points on it as the difficulty to identify and follow the acoustic stimuli.

In this experiment, the configurations about the locations of loudspeakers and sound sources were the same as those in the previous experiments. **Figure 8** shows the experimental configuration and subjects following the sequence. The distance between the loudspeakers and their heights were set to 3 and 4 m, respectively.

The three factors considered important to the performance of the experimental task were the type of sound source, the type of loudspeaker, and the patterns of emitting sound sequences in the third experiment. Two levels, voice and swept-sound, were set with respect to the type of sound source. In the same way with previous experiments, the phrase in female voice, "Here is an emergency exit" was used as voice sound and the acoustic stimuli whose frequency changed from 500 to 1000 Hz continuously was used as the swept-sound.

The two levels, a capacitor-type speaker and a dynamic range one, were set with respect to the type of loudspeaker on which the sound stimuli were emitted. The capacitor-type flat and the conventional dynamic rage speakers have different specifications for directionality, which is the property to focus audio and deliver clear sound

**Figure 8.** *Experimental configuration and a subject following the sound sequence.*

precisely where it is needed. In other words, the reduction in sound level through the capacitor-type speaker is smaller even when the reach is farther away because sound spread is smaller than the dynamic one. The capacitor-type one has higher performance than the dynamic range one in the specification of directionality. This factor was designed to evaluate whether the directionality of the loudspeaker affects the sound localization performance for a moving sound source.

The third factor in this experiment is the pattern of emitting sequences. **Figure 9** shows the emitting sequence patterns of sound, which are drawn as connections of consecutive column-wise and row-wise line segments. "S" and "G" in **Figure 9** indicate the start and goal points of each sound sequence. The sequence patterns are classified into five categories based on the number of turning points in themselves. There were 20 sequences (two sequences in conditions of the number of turning points and start-goal places), as shown in Figure 9. A sequence with one turning point means that the subjects turn for direction once during following it. The third experiment was finally designed under all the combination conditions of three factors (2 levels × 2 levels × 20 patterns) as described above.

## **4.2 Experimental procedure of experiment 3**

The sound source level of voice and swept-sound were set to 80 dB (A-weighted loudness level) at 1 m from the loudspeaker. The noise level was measured using an integrating average-type sound-level meter (LA-1441, Ono Sokki). The sequences of sound were emitted from the lower left (loudspeaker 21) or lower right (loudspeaker 25) to the upper right (loudspeaker 5) or upper left (loudspeaker 1) which were indicated by circle "G" are shown in **Figure 9**. The evacuation routes with one to five turning points are also illustrated by the solid and dotted lines in **Figure 9**, which were formed symmetrically with respect to the diagonal.

The subjects were seven students (six males and one female, 20–21 years old) with no hearing abnormalities during their annual medical examination. The subjects were instructed to follow the sound sequence at walking speed. The sequences of emitting

*Evacuation Guidance Assistance System Using Emitting Sound DOI: http://dx.doi.org/10.5772/intechopen.105223*

**Figure 9.** *Sound-spatial sequences provided to subjects.*

sound were randomly presented to them. In each trial the first point of the sequence was randomly chosen so as not to infer the emitting sequence pattern based on it. The subject stood up at the point under the loudspeaker 23, and identified the sequence of emitting sound and followed it.

The experiment using voice as the sound source was conducted first, and one using swept-sound was conducted two months later. In each experiment the subject performed the trial to identify and follow the sequence of sound that was emitting on two types of loudspeakers, the capacitor-type and the conventional dynamic range speakers. The half of subjects (five subjects) performed the trial using the capacitortype speakers at first and the one using the conventional dynamic range one after it. The remaining subjects (three subjects) performed the trial in reverse order with respect to the type of loudspeakers.
