There are so many topics I cannot wait to address! Before we get too deep into complex discussions of speech and hearing sciences, however, we need to establish a common base of knowledge to draw from later on. Therefore, several upcoming posts will address the basics of speech sound production!
Speech production is something many of us do every day. Whether it’s for one’s job or socialization, so much of our society is built around the voice. But how many of us can say we understand how the production of speech works beyond the basics? Why do we breathe in before we talk? What happens in the throat that makes the air vibrate? How does the passage through the mouth and nose shape and change the sound? And how does the human brain coordinate and execute the complex sequence of muscle contractions that results in the movement of teeth, tongue, lips and much more, to articulate speech?
If these are questions you're interested in exploring, this is the article for you!
The beginning step of producing the voice is respiration, or the act of breathing. Breathing in is referred to as inhalation or inspiration; breathing out is known as exhalation or expiration. This takes place in the lungs. The lungs reside in the thoracic cavity, along with the heart, esophagus, trachea, bronchi, and other important structures. The thoracic cavity is protected by the ribs and the surrounding musculature.
During inhalation, the diaphragm contracts, expanding the thoracic cavity by pushing our abdominal cavity organs down and out. The lungs expand to fill the empty space, which results in a pressure drop in our lungs. Due to the pressure difference between our lungs and our surrounding environment, air rushes in to fill the space (this is known as Boyle’s Law). The air travels into the lungs and reaches the alveoli, which transfer the oxygen to the blood in exchange for carbon dioxide.
Thanks to the heat our bodies produce, the air in our lungs begins to increase in temperature. As the air heats up, it expands and the pressure in our lungs increases (this is known as Charles’ Law. The lungs also begin to decrease in size due to wanting to return to a resting position (or elasticity), which increases the pressure as well. At this point, the air in our lungs is at a greater pressure than the pressure in our environment. Thanks again to Boyle’s Law, the air rushes back out of the body and out into the environment.
Tidal Breathing: Breathe in and out as calmly as you do when you're at rest, feeling the muscles activate when you breathe in, and how no force is needed to breathe out. Time how long it takes you to breathe in, and how long it takes to breathe out. The rates of inhalation and exhalation should be roughly the same (with maybe a nod towards longer exhalation).
Speech Breathing: The next time you speak to someone, pay attention to how different the inhalation and exhalation feel when compared to life breathing.
The takeaway: Tidal breathing (usually) feels different than breathing for speech. Tidal breathing is a cycle of roughly 40% inhalation and 60% exhalation, and the exhalation is passive, meaning no muscles are activated to do it. However, when breathing for speech, the cycle is roughly 10% inhalation and 90% exhalation!
DO Try This At Home!
By gently activating the muscles of inhalation alongside other muscles, such as the inner layers of intercostal muscles, one slows down how quickly air exits the lungs to a rate we can use for speech. This slower air travels up the trachea and through the larynx. It is here that the next stage of speech production occurs: phonation! We'll talk more about this next step in a later post. For now, let me know if you have any questions about breathing that were not answered in this post!