Another important consideration in designing a modelling approach is understanding the nature of the output required and its subsequent use. When the size of the acoustic domain is comparable to the wavelength of the sound being modelled then finite element (FE) analysis is favoured. An example of this modelling is the low-frequency response of a headphone speaker where the wavelength and acoustic domain are both centimetre scale.
Other approaches to model the sound field are used when the acoustic domain becomes large with respect to the wavelength. Boundary element method (BEM) provides a means by which of modelling large structures without the requirement of large numerical meshes (required by FE). An example of the use of BEM is the modelling of the acoustic output of wind turbines with 200m tip heights and their effect on local communities. Ray tracing and parametric equation approaches are also an efficient way to model the propagation of noise for point and linear sources, such as motorways and construction activity. Xi also use ray tracing and parametric equation approaches for modelling building acoustics, such as concert hall acoustics, and underwater noise and its impact on marine species. A diffusion equation approach is a very effective way of modelling acoustics of coupled rooms within a building can be used to improve office and residential environments.