|Welcome to Carolyn's blog! My name is Carolyn Michener and I'm a sophomore in the speech, language, and hearing sciences program at Boston University. This is my second year working at the STEPP Lab. Since I'm studying speech science and not engineering, I often have to do personal research to understand the more technical aspects of other lab members' projects. I'm writing this blog to help explain these projects to other individuals with little technical experience, or to those who are interested in learning more about the STEPP Lab.|
|Liz Heller Murray: Speech-language Pathologist, Voice Enthusiast, and Food Truck Connoisseur|
November 19, 2013
Liz Heller Murray is a Ph.D. student in the Boston University Speech, Language, and Hearing Sciences program. Her current research includes examining why some patients with normal looking vocal folds develop excess muscle tension in their larynx, a condition called muscle tension dysphonia. People with muscle tension dysphonia often sound strained or hoarse and raspy, as they are inappropriately using their muscles causing an altered quality to the voice. To determine how muscle tension dysphonia affects the vocal folds, it is helpful to talk about how normal vocal folds function. The vocal folds are two small tissues that abduct (move apart) to permit breathing and adduct (come together) to produce voicing. The muscles and cartilages of the larynx, or voice box, cause the vocal folds to move in this fashion. Check out a video of video stroboscopy of healthy vocal folds here. In muscle tension dysphonia, there is excess tension of the laryngeal muscles that causes the voice to sound so strained. You can see the extreme tension in this strobscopy. In the video, the vocal folds are partially obscured from view by the over-tensing muscles. However, when the individual breathes in and the vocal folds are abducted, we can clearly see that the vocal folds look normal, meaning that the physical, organic characteristics of the vocal folds have not changed. Research in muscle tension dysphonia is therefore very important because little is known about what causes the laryngeal muscles to become so tense without an organic cause. Liz chose to study speech-pathology because she believes that the voice is a very important component in our lives, and finds that helping clients properly use their voice is extremely rewarding. After completing her Ph.D., Liz hopes to find a job as a speech-language pathologist and researcher in a voice center. In her spare time, Liz, whose Patronus is a cat, enjoys watching How I Met Your Mother and hopes to one day travel to Bora Bora.
|Velopharyngeal Dysfunction: When Nasality of Speech Affects Intelligibility |
October 29, 2013
The velopharyngeal dysfunction (VPD) project is another one of my favorites because, like the RFF of Vocal Effort project (see post from October 1, 2013), it's a combination of the lab's engineering expertise and my interest in speech disorders. VPD is essentially nasalization of speech, particularly in children, and can make speech difficult to understand. The phonemes /m/, /n/, and /ng/ (as in sing) are considered to be nasal because air escapes through the nose, not through the mouth, when you say them. To feel this yourself, place your finger between your nose and upper lip and say "mom" and "dad". When you say "mom" you should be able to feel air leaving through your nose, whereas when you say "dad" air escapes through the mouth. During production of nasal sounds, the velum (aka the soft palate) opens to allow air and sound into the nasal passageway. In individuals with VPD, the velar port remains open even during the production of non-nasal sounds, causing hypernasality of speech. Check out some speech samples of hypernasal speech here. The VPD project includes asking subjects to wear a headset designed by lab members that has a microphone to pick up acoustic signals and a small accelerometer placed on the nose to read nasal vibrations. We collected data from healthy and disordered children using this headset to compare nasal patterns between the two populations. In the future, we hope to expand this project to help kids with VPD to learn to produce more intelligible speech.
|How Does Vocal Effort Affect Relative Fundamental Frequency?
October 1, 2013
This is one of my favorite projects in the lab because it directly involves the speech science behind voice disorders and engineering. Our goal is to verify if there is a link between vocal effort and the relative fundamental frequency (RFF) of an individual's voice. RFF is loosely defined as the fundamental frequency of the cycles before and after the production of a voiceless consonant. You can read more about RFF and voice disorders here. Confused? Try placing your hand against your throat and say "aaaaffffaaaa". You should be able to feel the vibrations of your throat during the vowel production but your throat should feel comparatively at rest during the consonant production. This is because when a sound is "voiced" the vocal folds within the voice box vibrate, but when a sound is "voiceless" the vocal folds do not vibrate. Each time your vocal folds open and close during a voiced sound a vocal cycle is produced. By taking the frequency of the vocal cycles before and after the voiceless consonant, we can find the RFF. We asked the subjects who are participating in the study to speak at different vocal efforts so we can determine if it changes the RFF. The subjects spoke in a normal voice, an easy voice, and a strained voice. The normal voice is the same level of effort you use when talking to a friend or a colleague. An easy voice is a voice that requires less effort to produce it. If you sing along to your favorite song on the radio, you're using an easy voice. A strained voice is produced by increasing the effort it takes to produce speech. One way to speak in a strained voice is to raise your shoulders and tense the muscles in your neck while speaking. Try reading a couple sentences of this post while speaking in this fashion. If you sounded like Batman meets Gollum, you've successfully produced a strained voice! We think that determining how the RFF changes between each type of vocal effort could become an effective tool in diagnosing voice disorders.