Speech is a skill that virtually everyone masters but few pause to study in detail; it certainly isn’t necessary to understand how speech is created – on a conscious level – in order to talk. But there are plenty of reasons to study speech. Curiosity is reason enough!
A quick internet search reveals a great deal of information about speech production. I’m not about to say anything that’s not already been said. Rather, my motivation for this post is to offer an introductory explanation alongside an analogy.
First, a bit of background.
The parts of our bodies that work together to create speech are commonly grouped into three subsystems:
- The respiratory system, comprising the lungs and all of the muscles responsible for their expansion and/or compression.
- The vibratory system, which is essentially the larynx, an organ in the front of the neck that houses the vocal folds. The muscles of the larynx are divided into two groups: the extrinsic muscles, which determine its position in the neck (you can feel it move when you swallow); and the intrinsic muscles, which determine the configuration of the structures within the larynx (like the position of the vocal folds).
- The resonating system, comprising the oral cavity (including the tongue, teeth, lips etc.), the space behind the oral cavity (the pharynx), and the nasal cavity.
Essentially, the respiratory system is responsible for moving air in and out of the body. The vibratory and resonating systems use this respiratory airflow to create speech in a two-stage process. The first stage is performed by the vibratory system. During exhalation, air travels from the lungs and through the larynx, where it is channelled through a v-shaped space between the vocal folds called the glottis. If our vocal folds are closed during exhalation, they will vibrate in the egressive airstream. Hence, the vibratory system earns its name. Vocal fold vibration is also known as phonation – a physiological and acoustic event, most simply understood as ‘the production of sound’. You can feel the vibrations of phonation by putting your hand on the front of your neck and saying ‘aah’.
The second stage is performed by the resonating system. As the (now audible) airstream continues through the vocal tract, the resonating system acts as a filter, modifying the acoustic properties of the sound. By moving the articulators like the tongue, teeth, and lips, we can change the shape of the vocal tract. Different configurations of the vocal tract create the many different sounds of speech.
So, the analogy…
The process of speech production in this two-stage process is much like the creation of a clay pot. In this analogy, phonation is the clay made available to the sculptor, and the articulatory movements in the vocal tract are the ‘hands’ with which the sculptor moulds.
I find this analogy particularly fitting when considering our ability to say the same utterance using different types of phonation. To give an (unsubtle) example, take those precious three words “I love you” – they can be shouted from the rooftops, or whispered into a lover’s ear. Same words; different phonation type. Much like phonation, there are different types of clay. The choice of clay is not inconsequential; clays of different colours and textures can be shaped into the same shaped pot, but each clay will produce a pot that is visually and textually distinct.
This analogy is useful too when considering different accents. Sculptors may have the same set of sculpting tools at their disposal (pointy tools, blunt tools, wires, scrapers, pinchers…), but may use these tools differently, in styles that have been developed after years of practice, influenced by the sculpting styles of those around them. Equally, we all more or less have the same body parts (vocal folds, tongues, lips…), but we produce speech using different ‘accents’, because of our different articulation ‘habits’ or styles, learned through socialisation.
This explanation is simplified, and the analogy perhaps a little indulgent… but I hope it is useful. I’m keen to hear your thoughts!