The estimation of an HRTF for a given individual is accomplished by means of
a coupled model, which identifies the dependencies between one or more images of
readily observable characteristics of an individual, and the HRTF that is applicable
to that individual. Since the HRTF is highly influenced by the shape of the listener's
outer ear, as well as the shape of the listener's head, images of a listener which
provides this type of information are preferably applied as an input to the coupled
model. In addition, dimensional measurements of the listener can be applied to
the model. In return, the model provides an estimate of the HRTF for the observed
characteristics of the listener.