An example is the performance of an electrostatic speaker with a variation the pre-stress applied to the oscillating membrane. The reduction of the pre-stress level will affect the low-end roll-off of the speaker and thereby changes the speaker’s frequency response. However, the pre-stress level will also affect distortion levels. A model of the speaker can have the pre-stress level parameterised between predefined minimum and maximum values and solved to determine the variation in frequency response and total harmonic distortion; and an optimum value thereby determined. More complex optimisation can be undertaken by parameterising more than one parameter and looking at the performance over a larger parameter space.