This paper describes existing wind turbine sound limits in Australian states and several other countries with similar constraints, how these were established and a method that could facilitate their harmonisation. Most existing limits appear to have been adopted to avoid sleep disturbance using data derived from sound sources other than wind turbines. This seems to have been a reasonable approach at the time of their adoption because of the paucity of other suitable data. More recently the concept of "annoyance" has been used to encapsulate negative reactions to wind turbine sound. Many studies have now demonstrated a significant relationship between annoyance and wind turbine sound level, whether or not sound was the major source of the annoyance. Thus there is a logical basis for now deriving a wind turbine sound limit based on limiting annoyance. This paper describes such an approach. The derived limit is compared to existing Australian and international limits. Its value lies within the range of these other limits. It provides a method for harmonisation of future limits based on direct assessments of human response to wind turbine sound.