Vocal Acoustics

EM sensor

There is a ton of research going on, using ISM frequency measurements of vocal fold motions in conjunction with vocal acoustics to vastly improve speech recognition, speaker identification, signal processing, etc. See the dozens of works listed on John Holzrichter's web site  www.johnholzrichter.com  

Here is the title and abstract of one of John's papers you can read (for free!), we cribbed Figure 1 from it, shown at the top of the page.

John F. Holzrichter at al, "EM wave measurements of glottal structure dynamics", Lawrence Livermore National Laboratory, 

Low power, radar-like EM wave sensors, operating in a homodyne interferometric mode, can be used to measure tissue motions in the human vocal tract during voiced speech. However, when used in the glottal region there remains uncertainty regarding the contributions to the sensor signal from vocal fold movements versus those from pressure induced trachea-wall movements. The signal source hypotheses were tested on a subject who had undergone tracheostomy 4 years ago as a consequence of laryngeal paresis,and who was able to phonate when her stoma was covered. Measurements of vocal fold and tracheal wall motions were made using an EM sensor, a laser-doppler velocimeter, and an electroglottograph. Simultaneous acoustic data came from a sub-glottal pressure sensor and a microphone at the lips. Extensive 2-D and 3-D numerical simulations of EM wave propagation into the neck were performed in order to estimate the amplitude and phase of the reflected EM waves from the 2 different sources. The simulations and experiments show that these sensors measure, depending upon location, both the opening and closing of the vocal folds and the movement of the tracheal walls. When placed over the larynx, the vocal folds are the dominant source. The understanding of the signal sources is important for many potential applications.