Notice of Obsolescence – Vox-EMA – Read more

The Vox-EMA (electromagnetic articulography) tracking system captures dynamic orofacial and articulatory movements. This information can be used for research in the rehabilitation of speech pathologies. Microsensors attached to the tongue, lips, jaw and face record 5DOF (five degrees of freedom) movements without line-of-sight occlusions. Up to 16 5DOF sensors can be used at once to produce a detailed model of transpired motion. Minimal latency and noise, combined with high temporal and spatial accuracy, ensure the fastest and most subtle of movements are recorded the instant they occur. When used with a microphone, the Vox-EMA will synchronize audio with kinematic measurements, providing researchers with rich data to correlate voice production to articulatory movement.With its intelligent hardware design, seamless audio synchronization, and intuitive software, the Vox-EMA puts the focus on fast, accurate data collection – not lengthy setup or post-processing.

One Solution, Many Different Speech Studies

The Vox-EMA provides a highly configurable, flexible measurement method for managing the unique data collection parameters of your experiment or clinical application. The biggest challenge of any speech study is not being able to see what’s happening inside the mouth. Using attached sensors, digitized 3D points and palate traces, the Vox-EMA reports and displays 3D measurements in the Vox-VRI software, providing visibility into previously unviewable articulatory movements.

What’s more, you can see these movements in real-time for immediate subject assessment. You can also automatically save a recording of the transpired movements (measurements) for a comprehensive analysis of research in the following areas:


  • Accent Modification
  • Apraxia of Speech
  • Dysarthia
  • Fluency Disorders

  • Oral Myofunctional Disorders
  • Parkinson’s Disease
  • Phonetic Disorders
  • Post-Stroke Aphasia

Measurement You Can Trust

The Vox-EMA tracks extremely fast and subtle movements with sub-millimetre accuracy and repeatability: sensors are tracked to a static positional accuracy up to 0.9 mm RMS; 6DOF reference disc up to 0.6 mm RMS.

Accuracy remains consistent when tracking at 100 Hz, 200 Hz or 400 Hz. Even if the subject moves, or if the sensors are out of sight, accurate tracking is continuously maintained.

The Vox-EMA system components, measurement volume, and sensors are factory (pre-) calibrated. There’s no need to manually calibrate the system prior to data collection. The accuracy and repeatability of 3D positions are validated using a coordinate measurement machine (CMM) within our calibration facility to ensure reliable measurement performance, for credible measurement results.

Vox-EMA Technical Specifications

5DOF Sensor Dome Volume (RMS)
• Position • 0.9 mm
• Orientation • 0.2°
6DOF Sensor Dome Volume (RMS)
Position 0.6 mm
Orientation 0.3°
Number of Sensors Tracked Simultaneously Up to 16 5DOF; up to 8 6DOF
Sample Frequency (Configurable) 100 Hz, 200 Hz, 400 Hz
Measurement Volume Dome (660 mm Ø x 960 mm Ø)
Field Generator 200 mm x 200 mm x 70 mm

Third-Party Hardware

• Optotrak Certus® from NDI*
• Microphone via audio DAQ/mixer


• Included with sample MATLAB® application code
• Real-time protocol to most clients

Measurement Volume

Some measurement methods are true but not precise; others are precise, but not true. The Vox-EMA provides discrete 3D measurements that are both true and precise, without the use of filtering, averaging or other black-box processing techniques.

Legal Disclaimer
NDI tracking and measurement products (listed below) are general metrology components that can be integrated into customer products, research experiments, and/or as components of medical devices that require precision measurement and tracking. While NDI components and technology can be integrated into original equipment manufacturer (OEM) medical devices, they are not specifically intended for a given application and, as such, have not been developed or manufactured in accordance with medical device standards.  It remains the responsibility of the OEM customer or end-user to determine and test the suitability of NDI components and technology for their intended use, including performing any required ethics approval, verification, and validation required to demonstrate suitability and compliance. System-level testing, certification, and validation are the responsibility of the original equipment manufacturer or the applicable end-user and should be completed prior to use of NDI products or technologies in any application.