Machinery sound quality can appeal to people's aesthetic sensitivity and thus affect the commercial value of a product. Experiments were conducted to evaluate the economic value of the sound quality of machinery noise. Stimulus cards for twenty-seven kinds of vacuum cleaner were presented to participants. Each card gave participants details of the characteristics of each vacuum cleaner with respect to six attributes such as manufacturer, system for sucking up dirt, price, and noise level (dBA) and sharpness (acum) of the machinery noise. Each attribute had two to five levels. For the attributes of noise level and sharpness, three levels were set up (64, 59, 54 dBA and 2.46, 2.21, 1.96 acum, respectively). Participants evaluated their preferences for each vacuum cleaner on a scale of "purchase/not purchase". Fifty students and 50 people over sixty years of age participated in these evaluations. Conjoint analysis was applied to the rating values. As a result, students regarded "price" as the most important. On the other hand, seniors regarded "manufacturer" as the most important. For both groups, the "machinery noise" attribute was slightly more important than the functional attribute "system for sucking up dirt". From this analysis, the partial utilities of each level for each attribute were also obtained. These values correspond to the partial regression coefficients in multiple regression analysis. For the "machinery noise" attribute, the partial utilities increased as noise level and sharpness decreased. Furthermore, the estimated value for a 5 dBA reduction was 25 EURO, and for a 0.25 acum reduction, approximately 27.6 EURO.