Recent research has found it useful to distinguish between the form and meaning of sounds. To investigate the relevance of meaning, naïve students and professional drivers listened to four levels of meaning neutralisation and four levels of spectral slope of recorded truck sound. Self-assessment of emotional reactions showed that professional drivers did not vary much in activation and rated over all lower activation than naïve participants whose affect ratings moved more or less along the annoyance correlation line in the upper left quadrant of the affect map. This gives some information about the importance of the source being recognisable and of previous user experience for product sound quality. It is further supported by that the overall difference between naïve participants’ and professional drivers’ ratings decreased with increasing meaning neutralisation. The methodology applied in the current study may be adopted to form homogenous panels of experts for sound evaluation.