Stevens' methodology in the investigation of speech sounds is organized into three steps. The first step is to use physics (mainly tube models) to model the shape of the articulators (e.g. the shapes of the front and back cavity, rounding or non-rounding of lips, etc).
Stevens' methodology in investigating speech sounds is divided into three stages. The initial stage employs physics (primarily tube models) to simulate the form of articulators (such as the shapes of the front and back cavities, lip rounding or non-rounding, etc.).