Sound quality is an important product attribute, which affects the power of competition in the market. Moreover, good sound quality can positively influence our life quality. To evaluate the sound of products, measurements of sound power levels are currently used. However the sound power does not characterize the customers' perception of product sound sufficiently. Within the scope of the Eureka Project 8684 Sound Quality, a sound quality study on tumble dryers was conducted. So far no sound quality index for tumble dryers exists that characterize the customer's perception of dryer sound. Therefore the aims of this study are to identify the perceptually important features of the tumble dryer sound that affect the impression of quality, to evaluate the perceived overall quality of various tumble dryer sounds and to define a sound quality index based on psychoacoustic metrics. To systematically approach to the above mentioned aims, first the tumble dryer sounds were recorded and the recorded stimuli were modified via digital filtering in frequency and time domains. Then the recorded signals were analyzed and their psychoacoustical metrics were calculated, in parallel a listening test to evaluate the sound quality was conducted. The results of the psychoacoustic analyses and the jury test were correlated and a sound quality index was developed.