A model for predicting the noise level of cross-flow fans has been developed. In this model, the relative air-flow velocities on the outside of the fan's impeller are used. The model is based on two assumptions : noise levels are in proportion to the relative velocities at the edge of the blade raised to the sixth power and the velocities on the outside of the impeller have an especially close relation to the noise level. Well established computational fluid dynamics model is used to obtain the necessary velocity-field data for this model. The noise levels calculated by this model are in good agreement with the measured noise levels of a test impeller. This confirms that changes in the noise level with changes in the flow coefficient can be well described by the model. It is concluded from these results that this simple prediction model is a very useful tool for speeding up of the development of silent cross-flow fans, since relative velocity data is readily a vailable from frequently executed computational analyses.