When Australia's interest rates fall relative to others', then our interest rates are providing lesser returns to investment than other countries are. Therefore, investment in Australia is less attractive, leading to capital outflow. When there is a capital outflow, there will be a lesser demand for the Australian dollar, thereby putting downward pressure on our currency.
Basically, with lower interest rates we will have:
- less foreign investment coming into Aus, and
- a depreciating exchange rate