Welcome to the fourth and final installation of our blog series on the speech mechanism! We have covered our respiratory system and airflow for speech in Part 1, creating voicing in the larynx in Part 2, and the resonance chambers in Part 3. We are now prepared to dive into some of the most motor-demanding and complex players in the speech system, our articulators.
Let’s begin with defining what the articulators and articulation actually are. In speech, these are the active and passive structures in and around the mouth that interact with the airflow from the lungs to transform the voice into individual sounds. They have one of the most skilled jobs in that they must move rapidly in a coordinated, accurate manner to produce sounds alongside each other to form words and sentences, a process referred to as co-articulation. Even though it may seem like there are breaks or separations between words when we talk, the auditory reality is that the ending sound of one word flows immediately into the beginning sound of the next. You can hear this more clearly if you listen to someone speaking in a language you are not familiar with it may feel like there is no way to pick out individual words because of this connected nature of speech.
To help us define the different types of consonants and vowel sounds in any language, linguists and speech pathologists consider the following three categorizations:
Place: Where a sound is produced within the mouth
Manner: How the sound is produced (usually in reference to how the airflow is restricted to create specific sounds)
Voicing: The vibration of the vocal folds (i.e. if they are “on” or “off” when producing a sound -see more on this in Part 2 of this series)
We will focus on standard English sounds and their corresponding aspects of place, manner, and voicing in this article, but every dialect, accent, and language will have its own unique repertoire. We will also discuss some examples of how dyspraxia can affect articulation for many nonspeaking people for each of the articulators.
One of the largest rigid structures in the mouth is the palate, a feature separating the mouth from the nasal cavity, consisting of both bony and soft tissue components. We subjectively divide the palate into three parts to help us further define the place of articulation for vowels and consonants. At the front of the mouth, just behind the teeth, is a bumpy, hard section known as the ALVEOLAR RIDGE, which makes up the first half of the hard
palate. Behind this is the smoother, convex portion. They are not actively moving parts in articulation, but they do provide contact or constriction points for the tongue to create sounds-we’ll dive into this more deeply later.
Taking up the rear is the third portion of the palate, which is composed of soft but muscular tissue called the velum. The velum is a moveable and more active articulator that primarily serves two purposes. Firstly, it closes off the opening between the nose and mouth to prevent food or liquid from entering the nasal cavity when we swallow. Secondly, when speaking, it moves quickly between its open and closed positions to direct airflow through the nose or the mouth. When air flows out of the nose, we create nasal sounds like /m/, /n/, and /ng/ as in “king”. When closed, we create oral sounds like /b/ and /d/. In fact, the differentiating factor between some sounds (ex. /n/ and /d/) is whether the air flows through the nasal cavity or oral cavity.
When a person experiences dyspraxia of speech, the rapid opening and closing of the velum during connected speech can be disrupted or difficult to initiate at all. This can mean sound errors, like producing an /n/ sound when trying to produce a /d/, or experiencing consistent hyper- or hypo-nasal quality when speaking. Think of the examples of Steve Urkel (hypernasality) and someone who has a bad cold (hyponasality), either of which can have effects on clarity.
From the palate, we move on to the next set of articulators, which are comprised of the lower jaw/mandible and the upper and lower teeth. Here, we have a mix of stationary and moveable articulators. While not the most active, the jaw is essential to note because it makes small changes in position to assist the other moveable articulators, and acts as an anchor for muscles of the tongue and larynx. The teeth, similar to the palate, are used as an occlusion point for more moveable articulators to create sounds like /f/ and /v/ (where the lower lip rests gently against the upper teeth) and voiced and voiceless /th/ (where the tongue tip protrudes between the upper and lower teeth).
For a nonspeaking/dyspraxic person, making these slight jaw adjustments can be difficult and result in issues with speech clarity, like distorted vowel sounds or unclear consonants.
From here, we move on to our only external articulators, the upper and lower lips. They are much more agile than our previous articulators and are responsible for many sounds: bilabial (“two lips”) sounds like /b,p,m/, labiodental (i.e., lip and teeth) sounds like /f,v/, and they contribute to many vowel sounds. For example, they can round to form /o/ as in “boat” and /u/ as in “boot” or retract for /i/ as in “feet.”
Given the mobility and timing requirements here, you can guess how dyspraxia may affect someone trying to recruit the lips for these sounds: many nonspeaking people struggle with vowel and consonant errors that require lip involvement.
Last but certainly not least, we arrive at the most agile organ of speech: the tongue. It moves backward and forwards, up and down, and sideways across the entire oral space and is responsible for most of the articulation work. Several muscles form the tongue, and much like the palate, we arbitrarily divide it into sections to help us describe how this complex organ contributes to vowels and consonants.
In Standard American English, all 20 of the vowel sounds and, as you can see in the photo above, 16 out of the 24 consonant sounds directly involve the tongue. The tongue tip, sides, middle, and back move rapidly to restrict, block, or direct airflow in various locations in the mouth to create differences in both places of articulation and manner. For example, the tip and/or blade of the tongue can contact the alveolar ridge behind the teeth, completely stopping air for a moment before releasing it to create the sound /d/: an alveolar “stop” sound. It can also move close to the alveolar ridge without actually touching it, creating a restriction where the air has to flow through-this creates the /s/ sound. /S/ is known as an alveolar fricative-it is produced near the alveolar ridge, and restriction formed by the tongue in this area causes turbulent and noisy airflow we call “frication.” We also use the alveolar ridge and the tongue tip to create the sound /l/ (as in “like”), which is a lateral alveolar liquid/glide sound-the tongue tip stays in contact with the alveolar ridge, but the sides of the tongue drop, allowing air to flow laterally off the tongue and create a fluid, vowel-like consonant sound.
All of these sounds are created in the same place (the alveolar ridge), but have different manners of articulation (stopping, frication, and gliding). By using a different part of the tongue and various occlusions to the airflow, we can add even more sound variations, like a velar stop (i.e.,/k/ or /g/).
The complexity only continues with vowels-you can try this yourself by just producing and listening to the vowels in “Feet”, “but”, and “caw”. The first vowel, “e”, tends to be produced closer to the front of the mouth and with the body of the tongue held higher. “Uh” is considered a more neutral vowel, with the tongue in a mid-position in the mouth, and “aw” tends to occur lower and towards the back of the mouth.
English is also a language that has diphthongs, or two-part vowels, like the /oi/ in “boy” or the /a/ in “ate” requires smooth movement from one vowel position into another.
For a dyspraxic person, being able to reliably and quickly make these kinds of tongue shapes and changes can be a major hurdle, resulting in muddy/unclear vowels and errors in manner and place for consonants. Here is an excellent video showing the movements necessary for just five of the vowels in English, which helps highlight just how much coordination is required for a single sound!
Another video of the complexity of connected speech; in this case, a German speaker.
If you are a nonspeaking person, the multiple hurdles of speech outlined here are likely no surprise for you. For those of us who can and do use speech to communicate. This compilation of blogs may be an eye-opening trek through a system we take for granted-and highlight why it is not as simple as we think! The big takeaways for anyone who has been with us through this series come down to this:
1. Speech is a complex fine motor process that involves multiple anatomical components moving together in a highly coordinated, rapid manner.
2. Access to speech is going to be variable and unique to each dyspraxic person.
3. Having access to alternate forms of communication that require less motor demand can allow dyspraxic individuals to participate more fully in their lives, and to set goals with their supportive loved ones, practitioners, and communication partners regarding if, when, and how they want to pursue speech as part of their communication tool box.
We thank all of you who have taken the time to explore this blog series and hope it has been enlightening, supportive, and educational. Please continue to follow the I-ASC blog page and to let us know topics that may be helpful to expand upon here!
Sincerely,
Bryana Williams M.S. CCC-SLP
I-ASC Registered S2C Practitioner
Sources:
http://marina-teachingandtranslating.blogspot.com/2013/06/the-speech-mechanism-how-are-sounds.html
http://my.ilstu.edu/~jsawyer/respiration3/respiration2_print.html
https://emedicine.medscape.com/article/1949369-overview
https://calleteach.wordpress.com/2010/01/10/sounds-of-english-nasals-liquids-glides/
Living in Atlanta and supporting non-speakers in Georgia and Nashville, Tennessee, Bryana Williams is a Speech-Language Pathologist and registered Spelling to Communicate Practitioner. She owns her own private practice and has, for the past two years, worked as part of the I-ASC S2C Professional Training Course as a mentor, Cohort Captain and continues to support I-ASC’s practitioner and CRP training initiatives through the development and improvement of training protocols. Bryana was introduced to Spelling to Communicate in 2014 during an outreach in Atlanta: “I immediately saw, over the course of just a few hours, students demonstrating their knowledge and communicative skills at a level that my traditional training had never allowed them to reach. I knew then that I had to change everything.” She subsequently has focused her career on learning from and with neurodiverse individuals, bringing her interests in teaching and communication to her current role as a member of I-ASC Leadership in expanding the professional training course and developing content.
