How Fluent Speech Is Produced - Speech Therapy Cumming GA
Posted on October 8, 2008
How Fluent Speech Is Produced
Speech begins with breathing, also called respiration. Your lungs fill with air, more air than you would inhale if you weren’t talking. You expand your upper chest and your diaphragm (belly) to get all this air in. Your lung pressure and respiration muscle tension increase.
Next, you release air through your throat, past your vocal folds (also called vocal cords). Your vocal folds are a pair of small muscles in your larynx. If you tense these muscles slightly, and release a little air, your vocal folds vibrate. This is called phonation. It’s also called the fundamental frequency of your voice. If you place your fingers across the front of your throat, then hum or talk, you can feel your vocal folds vibrating.
Adult men vibrate their vocal folds about 125 Hz (125 times per second). Women vibrate their vocal folds about 200 Hz. Children’s voices are even higher. This is too fast for your brain to control. Vocal fold vibration is the only muscle activity that your brain doesn’t directly control. Instead, phonation results from the coordination of respiration muscles with slight tensing of your vocal fold muscles.
The key word in that last sentence was coordination. Stuttering is largely a disorder of poorly coordinated speech production muscles.
If you tense your vocal folds too much, you block off your throat and stop air from escaping your lungs. This is a good when lifting heavy weights. By blocking your larynx muscles, you increase lung pressure, which strengthens your chest and you can lift more weight. Similarly, tires inflated to high pressure can carry a heavier car. But that’s what stutterers do when they talk, and it’s not a good idea.
The space in your throat above your larynx is called the pharynx. Above your pharanx are your oral and nasal cavities. These spaces create vocal resonation. This is like the echoing of a cathedral or tunnel. The unique shape of these spaces makes each of our voices sound unique.
Your jaws and lips, collectively called the articulation muscles, modify your voice into intelligible speech.
Vowels and voiced consonants (such as /b/ and /d/) are produced by your vocal folds, and modified by your articulation muscles (jaw, lips, tongue).
Other consonants are voiceless, such as /p/ and /t/, produced by your articulation muscles modifying airflow, without your vocal folds vibrating. When you whisper, you don’t vibrate your vocal folds. You just modify airflow with your articulation muscles.
Speech requires coordination of over 100 muscles. The average person speaks about 150 words per minute. Each word requires a different configuration of most of those muscles. Speech is our most complex, balanced neuromuscular activity.
From Wikibooks, the open-content textbooks collection