What is a good rehearsal technique for developing a performer's use of voice?

Whilst there are multiple rehearsal techniques that can be used to develop a performer's use of voice, a rehearsal technique which is simple to understand and explain is the limiting the rehearsal space.

Practiced by practitioners such as Katie Mitchell, limiting the rehearsal space reduces the amount of room in which the performers can move and use their physicality to communicate characterisation. Consequently, the performer is more dependant upon their use of voice to achieve this aim, hence they will focus more greatly on this aspect of their performance in rehearsal.