* Inaudible, high frequency sound waves are passed into tissues
* Waves reflect upon hitting an air boundary (e.g., in the oral cavity)
* Reconstructed echo pattern shows shape of structure(s)
* Used to assess the movement and position of the tongue, lips, and other articulators during speech important for diagnosis and treatment of various speech disorders (e.g., articulation disorders, apraxia of speech, dysarthria, resonance disorders such hypernasality or hyponasality, dysphagia, etc.)