SPAU 3304: 4-5 Notes
SPAU 3304: 4-5 Notes SPAU 3304
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This 3 page Class Notes was uploaded by Kimberly Notetaker on Tuesday April 5, 2016. The Class Notes belongs to SPAU 3304 at University of Texas at Dallas taught by Dr. Garst in Spring 2016. Since its upload, it has received 49 views. For similar materials see Communication Sciences in Linguistics and Speech Pathology at University of Texas at Dallas.
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Date Created: 04/05/16
THEORIES OF PHONATION - Finishing MyoElastic Aerodynamic Theory Role of Subglottal Air Pressure Subglottal Air Pressure Causes VF to separate Puff of air escapes (wave-like motion); more vertical; NOT abduction Vibration of VF > 100/sec Acoustic Characteristics of Phonation: Fundamental Frequency (F0 or F 0) o Fundamental Frequency = # of vibration cycle of the folds/sec o Perceived as pitch o Vibration also produces harmonics o F 0controlled by: Cricothyroid (CT) muscle contraction Thyroarytenoid (TA) muscle contraction Lung (Subglottal) pressure Glottal Spectrum: illustrating sound signal at the glottis o Periodic vibration o Fundamental frequency o Complex: Multiple frequencies are produced (harmonics) o Harmonics contribute to the quality of the voice **Sound produced by VF vibration does NOT represent what is ultimately heard. o Signal is further modified in the vocal tract (articulation & resonance) Intensity o Major determinants: Lung pressure (higher pressure, greater intensity) More air escapes in the open phase (resulting in a greater intensity of the signal) Vocal fold closure (really breathy, hoarse voice) Vocal tract resonance Key Pieces: Phonation o Subglottal air pressure Air pressure below the folds must exceed the pressure above the folds Subglottal pressure is mechanism for separating of VF during vibration Bernoulli effect relevant for bringing VF together (closing) during vibration o Myoelastic-Aerodynamic Theory VF drawn together by the Bernoulli forces Pushed apart by the lung pressure. VF physical properties are key (stiffness, histology myoelsastic properties) Allows them to be acted upon by the aerodynamic forces. » Physical properties (how stiff/tense/laxness) of vocal folds are under neural control of muscle contraction o Tensing (pitch perceived higher) o Abduction/Adduction » VF vibration is a passive event resulting from the M-A interaction, not neural driven. (due to subglottal pressure + M-A Theory) Cover-Body Theory (Specifically vocal fold construction) Vocal Fold Histology: o Different layers allow for changes to pitch and loudness Cover-Body Model (Hirano) o Cover: Mucous membrane Least stiff o Body: Mostly muscle More stiff o Cover and Body have different vibratory properties. o Intrinsic laryngeal muscles determine how tightly the body and cover are connected. (correlates to pitch changes) Phonation Function and the Mucosal Wave: Any extra mass will alter normal wave Graphic Descriptions of Speech: Speech Analysis o Conversion of sound waves to visual representations o Can be inspected, measured in various ways o Related to articulatory gestures that produced them 1. Waveform o A waveform displays: » Changes of air pressure over time » Complexity of the acoustic patter o Used for: » Temporal Measurements o Not appropriate for frequency analyses o Would NOT be able to tell the phonemes in a waveform o Fourier analysis (mathematical technique) analyzes the speech waveform Plots frequencies: Spectrum 2. Spectrum / Spectral Plot o Frequency-by-amplitude display o No time dimension 3. Spectogram o Displays all spectra computed for the speech waveform o X-Axis = Time o Y-Axis = Frequency (lower towards the bottom) o Darkness of tract = Intensity