The vocal folds within the larynx vibrate during voiced (pitched) speech and singing, and their vibration frequency can be altered resulting in pitch variation during speech and different notes when singing. Monitoring vocal fold vibrational activity is not easy, because they are within the neck. EGG and ELG are measurement techniques that enable the vibration of vocal folds to be monitored noninvasively in vivo without disturbing the speech or singing of the subject.