# Design and Implementation of a Semantic Information Expression Device Based on Vibrotactile Coding
## 5 Discussion  
In this paper, three types of experiments were conducted to explore the degree of usability of the device. The first one was the testing of the vibration intensity and the accuracy of vibration position recognition when selecting the vibration encoding scheme. The objectives were to find the vibration intensity that is suitable for the device and can be used without discomfort, and to allow the user accurate recognition of the vibration position as well as the increase in the speed of Braille reading, respectively. The results of the former test showed that 0.2 and 0.3 were the vibration intensities that were comfortable for the user. Since there were two suitable vibration intensities, a comparison experiment was conducted on the latter. A comparison was made between using only one vibration intensity (0.3 was chosen) and two vibration intensities on a Braille cell to see which option participants used to achieve higher recognition accuracy for Braille vibration dots. The result of the test showed that the recognition accuracy was only 72.50% when one vibration intensity was used and 93.75% when both strong and weak vibration intensities were used. Thus, the final encoding scheme was chosen to include both strong and weak vibration intensities. In short, for users with different levels of Braille, in order to simplify the user time of learning how to use the device and to increase the efficiency of its use, the device was designed with a coding scheme that uses only consonant and vowel symbols as the spelling rules for the Chinese characters and omits the tone symbols (the absence of the tones does not affect the reading of the Braille sentences). For users with different tactile sensitivities, the Braille cells were designed to have two vibration intensities to increase the user sensitivity to vibration. The intensity of the vibration was tested to be clearly perceived by most people and produced only a small amount of numbness. However, if there is a user with very low sensitivity, we will specially customize a device to suit their vibration intensity based on their perception threshold. The second type of experiment was a test experiment in which participants learned about Braille and device usage. The learning process was set up because the selected participants were sighted school students who had never been exposed to Braille before. The Braille learning phase took five days, and then the subjects' rate of memorization of Braille characters was examined. The test results showed that each participant's memorization rate was 90% or higher, indicating that the subjects could carry out the device usage learning process. In this process, the subjects spent five days learning the vibrotactile expression of the device's consonant characters, vowel characters, and 36 Chinese characters. In total, 12 of the 36 Chinese characters used to test the learning outcomes were tested for recognition rate. The result was 90.8%, which indicated that the users were familiar with the device and Braille characters.The next task was to evaluate the usability of the device through Braille recognition accuracy test experiments. However, to limit the subjects' touch-reading and recording time, the test of time spent was conducted along with the recognition rate test. The results indicated that the approximate duration was 9.47 s per Chinese character. However, this result tends to be subjective and cannot be used in the evaluation of reading speed. In addition, the participants learned the Braille characters and the device usage for only 5 days each, which is biased toward short-term memory. And the subjects had different learning efficiency and memory rates. Therefore, it is possible to improve recognition accuracy and reading speed with practice. It is also worth noting that Braille learning and device usage learning are both part of the learning process.