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Breathing Part for voice and speech production
How do humans produce sound?
What is the point of this section?
To determine how speakers can differ from each other, and the kinds of things they can vary that convey information to listeners. Listeners gather information about the organism from sounds it produces, so it's useful to know how those sounds are actually related to the body that produced them.
The human vocal organs
Phonation requires:
a source of power (to set molecules vibrating); a vibrating structure to convert aerodynamic power to acoustic energy; a filter to shape resulting output.
In humans, these are the lungs, the vocal folds, and the supraglottic vocal tract.
The human vocal tract
Phonation is not the original function of these structures.
The lungs are used for respiration (aka exchange of gasses--out with carbon dioxide waste, in with new oxygen), smell, and thermoregulation. The larynx protects the airway, and provides a rigid frame for heavy lifting. Supraglottic structures are used for eating, smelling, and so on.
Breathing
The lungs provide most of the raw power for speech and voice. Speech breathing requires some changes to regular respiration.
Prolonging exhalation so that more than one word can be produced on a single breath.
We'll start by describing normal breathing, then talk about how we change our behavior to speak.
Respiratory anatomy
Breathing uses the lungs, chest wall, and abdomen. The lungs are a complex branching network of air passages that end in millions of spongy, elastic air cells.
No muscles of their own Supported by diaphragm Contained by 12 pairs of ribs
The chest wall
Between lungs and ribs are tissues called pleura.
One pleura (visceral pleura) runs between the lung and the ribs. A second (parietal pleura) lines the chest wall. The pleura doubly seal the lungs. A small amount of fluid lies between the pleura, so they can slide against each other, but not pull apart. The pleura link lung tissue to the ribs, so that when the rib cage elevates/compresses, lung tissue goes with it.
Changing the shape of the chest cavity
Three primary muscles of respiration
The diaphragm The internal intercostals the external intercostals.
Function: By changing the shape of the chest cavity, these muscles create positive/negative air pressure in lungs.
The diaphragm
A dome-shaped muscle Contracts downwards When it contracts, the dome flattens out, increases size of thoracic cavity When it relaxes, it returns to rest position and reduces the size of the thoracic cavity. The most important inspiratory muscle
External intercostal muscles
Run from the bottom of one rib to the top of next lower rib Serve to elevate ribs
Contraction moves ribs like a bucket handle-- pulls them up and out
Muscles of inspiration because they expand the chest cavity
External intercostal muscles
The internal intercostal muscles
Run from the bottom of each rib to top of the next higher rib Outer parts lower ribs, are expiratory muscles. Compress ribs against chest wall.
Internal intercostal muscles
Two principles of aerodynamics
Boyle's law: Pressure and volume are inversely related in a soft walled enclosure at a constant temperature. Air will always flow from a region of high pressure to a region of low pressure.
What these laws mean for breathing
The respiratory muscles change the shape of the lungs, so that pressure changes and air flows in and out. In quiet respiration, when muscles act to increase the volume of lungs (by lowering diaphragm or raising rib cage), pressure in the lungs decreases, so if airway is open, air flows in through the nose/mouth. When the lungs are compressed by raising the diaphragm or lowering the rib cage, pressure in the lungs is higher than outside, so air is forced out of lungs.
Quiet breathing vs. speech breathing
Inspiration takes about 40% of the cycle in quiet breathing. The lungs are elastic tissue and have recoil forces.
The contents of the abdomen will also tend to press upward on diaphragm at end of inhalation, contribute to recoil.
In quiet breathing, we use muscular activity to expand the chest cavity for inspiration, but expiration is mostly passive (thanks to recoil forces).
Breathing for speech
Inspiration lasts only about 10% of cycle. We usually inhale more air when planning to talk than in quiet breathing. Speech requires relatively constant pressure below the vocal folds to keep them vibrating. So:
Typically need to brake the elastic recoil of the lungs during exhalation.
Keeping pressure constant for speech
Lung pressure is determined by a combination of recoil forces and muscle pressures. In the absence of muscular effort, the exact pressure delivered to the vocal tract will depend on the volume of air in the lungs. When the lungs are full of air, the relaxation pressures are big, but when the lungs are near their resting size, the system won't deliver much pressure/flow, because the pressure in the lungs is near atmospheric pressure.
Some demonstrations
Take deep breath, just relax
Air rushes out unless active resistance is applied.
Take deep breath, close glottis and hold breath, relax ribs
Feel the pressure?
Take deep breath, open mouth, don't close glottis, but keep air from rushing out
Feel muscular effort required?
Balancing recoil and muscle activity in speech breathing
In order to maintain the relatively constant pressure needed for speech, we need varying levels and types of active muscular effort to interact with the varying recoil energy of the respiratory system. Both inspiratory and expiratory muscles are used in expiration.
How do we this
The inspiratory muscles (diaphragm and external intercostals) stay active when the lungs are full and brake the recoil pressures. As recoil forces decrease, need less braking When lungs reach resting configuration, active expiratory effort is needed to expel further air and continue speaking.
Use abdominal muscles, back muscles, internal intercostals
Balancing inspiratory and expiratory effort
Summary: Speech breathing
Details, details
Breathing in speech can be very complicated.
Respiratory activity is associated with changes in loudness Demands of particular segments (/h/, for example...) Differences between individuals Effects of age, body type/shape, posture Differences across languages?
Summary
Under normal conditions, air from the lungs provides the power for voice. Air flows in and out of the lungs because changes in the volume of the chest cavity cause changes in air pressure relative to the outside atmosphere.
Air flows into the lungs when the internal pressure is less than the outside pressure, and it flows out when internal pressure is higher than outside pressure.
Summary, part II
The inspiratory muscles (diaphragm, external intercostals) expand the chest cavity during inspiration. Elastic recoil, gravity, and active muscle activity (internal intercostals, abdominal and back muscles) may all be involved in exhalation, depending on how much air is in the lungs and how the internal pressure compares to the external pressure.
Summary, part III
Both inspiratory and expiratory muscles may be used to control the amount of air that is delivered during speech.
Part II
Introduction to the scientific literature: How to read a research paper
Scientific method
Method for development of knowledge about general truths
Collection of data through observation and experiment Experimental research
Experimenter manipulates variables, observes effect on other variables under controlled conditions Drawing conclusions based on analyses of data
The importance of theory
A theory is a set of interrelated concepts, definitions, and propositions that presents a systematic view of phenomena by specifying relations among variables, with the purpose of explaining and predicting the phenomena.
Why we need theory
A theory:
Synthesizes available empirical evidence into a coherent explanation Reduces the data to the minimum number of terms Should account for all the data in the domain and make predictions about additional phenomena not yet observed, which means
Theories are testable and can be supported or falsified.
What is a hypothesis?
A kind of tentative theory Looks back at available data and makes a specific prediction about something that has not been observed yet
The first step in research
State the problem to be investigated Review previous research Explain why this question is important Explain relationship to theory and what predictions are made by the theory
This amounts to a rationale for the study, and should make it clear what is being studied and why.
Step 2: Determine the method to be used
Ideally, the variables selected and the design used will follow logically and elegantly from Step 1.
What is being measured? How is it related to the hypotheses? The DEPENDENT VARIABLE. What is being controlled? How is this related to the hypotheses? The INDEPENDENT VARIABLE.
Cause and effect
Because in an experiment we observe how one thing (the dependent variable) changes as a direct result of our manipulations of something else (the independent variable), an experiment can be used to demonstrate cause and effect. The independent variable is the cause; the dependent variable is the effect.
Research Step 3: Present the results
How did the value of the dependent variable change for the different levels of the independent variable?
Usually, this is demonstrated through statistical analysis.
Research Step 4: Draw conclusions
Did the results support the hypothesis? Are they consistent with previous findings? What new questions do they suggest?
Parts of a research paper
The structure of a research paper follows directly from the scientific method.
Title Abstract Introduction Methods Results Discussion
Title
Should be pretty brief Should not be too cute Should tell you what the paper is actually about
Abstract
Summarizes purpose, methods, findings, and significance of the research. Usually limited to < 200 words.
Introduction
Introduces the problem being studied.
What are the authors trying to find out, and why? (statement of problem) What gap in our knowledge are the authors trying to fill? Why does it need filling? (review of literature; rationale for study) What guess do the authors have about the answer? (hypothesis)
Methods
Detailed description of what was actually done Explains how the concepts under study are related to the empirical variables Should tell readers enough that they could replicate the experiment
Results
Qualitative and quantitative analyses of findings
Includes both statistical analyses and verbal descriptions of how the experiment came out, framed in terms of the hypotheses stated (hopefully!) in the introduction.
Discussion
Interpretation and speculation about the results Relates findings to hypotheses
Did they find what they expected?
Theoretical implications
Are results consistent with predictions, or do they suggest something is wrong with the theory?
Relationship to previous research
Any discrepancies?
Implications for future research
What comes next?
Next time
The larynx and sound production How to find scientific papers on a specific topic