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Research paper : Development and standardization of accessible design technologies that address the needs of senior citizens (K. Kurakata, et al.)−16−Synthesiology - English edition Vol.1 No.1 (2008) factor can be set, and hearing characteristic can be broken down finely and studied for each condition. However, such piecemeal knowledge is not useful in actual design. The process of “integrating” individual research results into one methodology is essential for completed design technology.Also, if the goal is the development of a technology that can be used effectively in actual practice, the result should not be researcher’s self-indulgence. Design precision can be improved limitlessly by using complex design method and by creating intricate model of human characteristics. However, the more precise the model, the range of application becomes narrower. This will not lead to the development of technology that can be applied to diverse domestic environments. Moreover, good precision and usability of method often conflict with each other. Even if it is a good design technology, it is meaningless unless it is used widely in actual practice.At the drafting stage of the standard, studies are conducted from aspects of academic accuracy and technological efficacy. The comments of on-site technologists as well as researchers are incorporated to create a standard methodology. The method standardized in this manner is expected to be used as a tool in actual design in wide-ranging fields over the long run.3 Auditory signal of consumer product and its problem“Auditory signal” discussed in this paper is sound emitted by the product itself or by the remote controller to notify the user of the operational status of the product. This includes sound set off as feedback when pressing a button on the control panel, sound to notify the end of action of the product, or sound to notify operation error or abnormality of the device. The usability of the product is improved and the occurrence of improper use can be lowered by appropriately designing auditory signals.However, conventional auditory signal did not necessarily function as intended, and many became sources of claims from the users. The content of the claims can be roughly divided into two (Figure 1). (1) Cannot hear the signal: “I thought the signal went off but couldn’t hear it”. (2) Do not understand the meaning of the signal: “I can hear the signal, but don’t know what it’s supposed to mean”.In designing auditory signals, three levels of adjustment can be made acoustically: (a) frequency (pitch of sound), (b) sound pressure level (volume of sound), and (c) time pattern (time change of sound). If the auditory signal was appropriately designed on each level, aforementioned claims could have been avoided.Inability to hear the auditory signal is a problem caused by inadequate selection of frequency and sound pressure level[4]. Human hearing declines gradually with aging. Elderly people with reduced hearing may not be able to hear sound that can be heard by young people. On the other hand, inability to understand the meaning of the auditory signals is because the signals were set off with different time patterns by product types and manufacturers[5].To solve this problem, the Association for Electric Home Appliances proposed to establish JIS S 0013[6] in 2002 to set frequency and time pattern of auditory signals. In this standard, it was recommended that high frequency sound that cannot be heard by the elderly should not be used, and specific time pattern should be used for auditory signals with certain contents. Hence, frequency and time pattern, two of the three factors that must be addressed when designing auditory signals, were standardized.The remaining issue was sound pressure level. If volume of the auditory signal is raised, the elderly with reduced hearing will certainly be able to hear. However, it may become a “noisy” sound for young users. Also, there is the issue of domestic sound in the place where the products are used. Auditory signal that can be heard in a quiet place may not be heard in the presence of interfering noise. Moreover, individual differences exist in the level of hearing ability, and the difference is notable in the elderly. The problem of volume setting of auditory signals was raised during the draft review of JIS S 0013, and it was an issue for which solution was strongly sought by consumer organizations and representatives of challenged people’s organizations. However, the matter was put on hold since it was not easy to find an appropriate volume setting that could be heard readily by both elderly and young people in various domestic situations.Fig. 1 Problems of auditory signals and issues to be resolved.Three levels of auditory signal design(a) Frequency(b) Sound pressure level(c) Time patternFactors that must be addressed to solve problem(i) Decreased hearing due to aging(ii) Interference by domestic sound(iii) Presence of individual differenceProblem of auditory signals(1) Can’t hear!(2) Don’t understand!

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