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).
The investigation by Stevens involves a three-step methodology for analyzing speech sounds. The first step utilizes physics, particularly tube models, to depict the configuration of articulators (for instance, the forms of the front and rear cavities, as well as lip rounding or lack thereof).