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SPPA 4030 Speech Science. Stephen M. Tasko Ph.D. CCC-SLP. Topic 1: The Speech Chain. Learning Objectives Outline the general sequence of biological/physical events that occur from speech formulation to speech perception.
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SPPA 4030Speech Science Stephen M. Tasko Ph.D. CCC-SLP
Topic 1: The Speech Chain Learning Objectives • Outline the general sequence of biological/physical events that occur from speech formulation to speech perception. • Describe the different types of information content embedded within the speech signal. • Know and describe the different branches of physics and biology used to inform basic mechanisms of speech production and perception.
What information is embedded in the speech signal? • Phonetic information • Affective information • Personal information • Transmittal information • Diagnostic Information
Physics Acoustics Aerodynamics Kinematics Dynamics Biology Anatomy Gross anatomy Microscopic anatomy Molecular biology Neuroimaging Physiology Electrophysiology Branches of science employed to understand speech communication
Physical Quantities ReviewAn Independent Learning Activity Learning Objectives • Distinguish between basic and derived units • Distinguish between scalar and vector quantities • Define a range of derived quantities with special emphasis on displacement, velocity, acceleration, force, pressure, intensity, resistance and their physical relationship
Assignment 1 • See Assignments section of course website • Due September 12, 2013
Topic 2: The Source-Filter Theory of Speech Production: An Introduction Learning Objectives • Outline the key assumptions of the source filter theory of speech production • Distinguish between the source signal, filter characteristics, and the output signal • Use a range of examples to demonstrate understanding of the source filter theory • Distinguish to role that different vocal tract structures play in speech sound generation and speech sound filtering
Producing Speech • The vocal tract can be conceived as a set of interconnecting tubes and valves. • Speech production is achieved through the systematic regulation of air pressures and flows within the vocal tract.
Source-Filter Theory of Speech Production • The sounds we hear as speech is the product of a sound source that has undergone filtering by the vocal tract • source and the filter may be considered to be independent of each other
Vocal tract is a tube that can vary its shape From Titze (1994)
Source Filter Theory Speech (What We Hear) Filter (Resonator) Source (Phonation) Frequency Response Curve Input Spectrum Output Spectrum
Different Source, Same Filters White Noise
Different Source, Same Filters (Non-Human)If it quacks like a duck…
Source-Filter Theory Applied: The Talkbox http://www.youtube.com/watch?v=YS3gAVNlceg
Topic 3: A Brief Review of Physical Acoustics Learning Objectives • Outline the physical processes underlying simple harmonic motion using the mass-spring model • Describe the molecular basis of sound wave propagation • Define the key characteristics of sinusoidal motion including • Amplitude: instantaneous, peak, peak-to-peak, root-mean-square (RMS), the decibel scale • Frequency/period including units of measure • Phase • Wavelength • Briefly describe the relation between the sine wave and uniform circular motion • Outline the relationship between the frequency and wavelength of a sound wave
Mass (inertia) Newton’s first law of motion Opposition to acceleration/deceleration Elasticity Opposition to displacement Rest position Recoil force Friction Spring Mass Model http://phet.colorado.edu/en/simulation/mass-spring-lab
What is sound? • It may be defined as the propagation of a pressure wave in space and time. • Sound must propagate through a medium
Medium is composed of molecules Molecules have “wiggle room” Molecules exhibit random motion Molecules can exert pressure A B Sound-conducting media
Model of air molecule vibration (Time 1) Air molecules sitting side by side Rest positions
a b c d Time 1 2 3 4 5 Distance Model of air molecule vibration
Time 1 2 3 4 5 Distance Wave action of molecular motion
Amplitude waveform Position Time
Amplitude waveform Amplitude Time
Where is pressure in this model? Time 1 2 3 4 5 Pressure measuring device at a specific location
Pressure waveform + 0 Ambient Pressure Sound Pressure - Time
Measuring Sound • Amplitude • Frequency • Phase • Wavelength
Measuring Sound: Signal Amplitude Ways to measure it • Instantaneous • Peak • Peak-to-peak • Root mean square (RMS) • Decibel –see later + 0 Sound Pressure - Time
Measuring Sound: Signal Amplitude • Root mean square (RMS)
What units do we use to measure signal amplitude? • Pressure: Force/area • Intensity = Power/area where power=work/time & work=Force*distance • Intensity is proportionate to Pressure2
Brief Review: The decibel scale • decibel scale typically used to represent signal amplitude • Many common measurement scales are absolute and linear • However, the decibel scale is relative and logarithmic
Absolute vs. relative measurement • Relative measures are a ratio of a measure to some reference • Relative scales can be referenced to anything you want. • decibel scale doesn’t measure amplitude (intensity or pressure) absolutely, but as a ratio of some reference value.
Typical reference values • Intensity • 10-12 watts/m2 • Threshold for normal hearing at 1000 Hz • Sound Pressure Level (SPL) • 20 micropascals
However… • You can reference intensity/pressure to anything you want For example, • Post therapy to pre therapy • Sick people to healthy people • Sound A to sound B
Linear vs. logarithmic • Linear scale: 1,2,3… • For example, the difference between 2 and 4 is the same as the difference between 8 and 10. • We say these are additive
