The production of speech sounds, in which the acoustics results from the production process, entails coordinated action of the respiratory system to generate the air stream conditions needed for vocal fold vibration at the larynx, and complex neuromuscular control of the vocal tract articulators - such as the tongue, lips, jaw, and velum - that shape the vocal tract continuously through time. When we speak, we have access to a large variety of signals that inform us about the current state variables of the production process. These somesthetic signals include motor commands available as copies of efferent motorneural commands, proprioceptive signals that for example give access to muscular elongation or acoustic structure via tissue vibration and haptic signals delivered by surface tissues, as well as exteroceptive acoustic information delivered by the ears. When we speak, the interlocutor has access to exteroceptive acoustic and visual information about our articulation. Thus both speakers and listeners have access to a great variety of redundant and complementary information associated with speech movements. In this chapter, we describe and discuss approaches to examining the visible characteristics of speech production and their link with other sensory information, in particular articulation and acoustics.