How do physiological measures of speech differ from acoustic measures?

Physiological measures of speech are considered to capture direct speech movements because they involve the monitoring of actual physical processes involved in speech production. This includes the observation of muscle activity, movements of the articulators (such as the tongue, lips, and vocal folds), and respiratory dynamics. Techniques such as electromyography (EMG), ultrasound, or motion capture provide insights into the biomechanical aspects of speech, allowing researchers and clinicians to understand speech production at a deeper physiological level.

This differs from acoustic measures, which focus on the sound waves produced during speech. Acoustic analysis includes the evaluation of sound frequency, intensity, and other characteristics via tools like spectrograms, which analyze recorded audio but do not provide information about the underlying physiological processes. By capturing direct movements, physiological measures add a layer of detail that is critical for understanding how speech is produced and how disorders may affect these processes.