* 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 ď 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.)