Polymeric gears are considered as being low-noise' components because their low modulus makes them resilient when the teeth come into contact. However, this does not account for the tribological noise generated as a result of the interacting tooth flanks. These are important considerations where high-precision motion control and low noise are required, for instance in high-quality printing transports. In addition, the identification of the source of acoustic emission from polymeric gears is necessary to completely understand their operation and give the possibility of design improvement. This paper investigates how the generated sound frequency spectrum is influenced by the various polymeric gear materials and operating conditions. The evolution of the frequency harmonics can be seen with progressive alterations in both speed and load. Results also demonstrate the influence of increases of surface roughness, wear and temperature on the respective sound power levels. In addition, effects of fibre reinforcement, geometry and material show that the tribological properties of gear materials can be used to predict noise generated and the significance of inaccuracies in polymer gear trains. Erroneous operating conditions were also identified from the generated spectra, suggesting a potential use of noise frequency analysis as a form of online error monitoring. (C) 2011 Elsevier Ltd. All rights reserved.