This article concerns a study of the spur gear noise (i.e. sound pressure level) of automotive gearboxes. The aim is to verify a direct correlation between transmission error and noise emission of a gearing. The article includes a description of some gearbox noise sources and focuses on the gears itself, which is a main source of vibration and noise. A risk analysis is performed to assess the factors influencing gear noise, to show a significance of transmission error. The main part of this article, however, concerns experimentally identified transmission error and its correlation with measured noise.