An emotional quality is a product quality that is evaluated by the customer’s subjective impressions, feelings and emotions. In the design of emotional qualities, one of the most important and difficult issues is setting quantitative evaluation criteria to evaluate such qualities. The customer’s sensitivity towards such qualities is diverse and latent. In our previous study, we proposed a quantification method of emotional qualities with attention paid to its diversity [1]. The method analyzes the diversity of emotional qualities and formulates their evaluation criteria based on the results of sensory tests. The authors formalized several emotional qualities expressed by adjectives using the proposed method with existing products. However, the variety of existing products was limited. The obtained evaluation criteria may not cover a design space where future designs would appear. In this paper, we propose a method to cover such untouched design space using composite samples in order to extract a potential factor of emotional quality for the future design. To create such a composite sample, we set efficient design features that take into consideration the completeness of design space and the diversity of a target emotional quality. In the method, we conduct two sets of sensory tests. One is using only existing design samples and another is using composite samples. We compare the results of the two tests in order to examine the repeatability of emotional scores among different sets of subjects and changes introduced by adding created samples. We apply the proposed method to extract potential emotional factors of product sound quantify. Using results of the sensory test with the created sound samples, we found two emotional evaluation factors. The first factor negatively related to loudness. The second factor related to lower sharpness and the existence of a perceivable peak tone around 500Hz. Most product makers are aware of the need to reduce loudness, i.e., the first factor. We found the second factor as a new evaluation criterion.

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