The usage of electric motors at cars and household appliances increases and the sound quality of them is becoming more and more important. Their noise contains various tonal components at low and high frequencies and in some cases these tonal components are modulated. Mostly the frequency of tonal components are rotational speed dependent. Therefore psychoacoustical parameters, such as tonality, sharpness, fluctuation strength, roughness and loudness, can be used to describe their perceptual characteristics of electric motor sounds. Whining, rattling, roaring, booming and hum are some verbal descriptors of various kind of electric motor sounds. The aims of this study are to evaluate the perceived annoyance of small electric motor sounds and to identify the perceptually important features which are relevant to the quality impression. To systematically approach to these aims, first the electric motor 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.