Which statement is true for voltaic cells?
a) Electrons flow from the anode to the cathode.
b) Electrons flow from the more negatively charged electrode to the more positively charged electrode.
c) Electrons flow from higher potential energy to lower potential energy.
d) All of the above
PRODUCTION and PERCEPTION of VOWELS: Part 1: Resonance Speech Sounds Vowels: o Produced by relatively free air passage o Through the larynx and oral cavity o Nucleus of a syllable Consonants: o One (or more) areas of vocal tract narrowed by some degree of constriction (partial or complete) Three Sources of Speech Sounds 1. Nearly Periodic Complex Waves (fundamental frequency w/ harmonics on top of it) » Source = vocal fold vibration » All vowels, many consonants 2. Continuous Aperiodic Waves » Source = turbulent flow through a supraglottal constriction (noise) » Many consonants, such as /s/, /f/ 3. Transient Aperiodic Waves » Source = rapid pressure change » Some consonants such as /p/, /b/ Acoustic Theory of Speech Production AKA Source-Filter Theory » Assumptions: o What we hear coming out of someone’s mouth is the consequence of The generation of a sound source Filtering of that sound source via the vocal tract’s resonant properties o The source and filter (vocal tract) operate in a largely independent manner. o Different postures change the shape of the resonator. o Can use acoustic signal to gather info about vocal tract position/features. Spectral Characteristics of the Source Sound from Larynx: Vibration rate determines fundamental frequency and harmonics Acoustic Characteristics of the Source: IDEALIZED glottal volume velocity = volume of air flowing through the glottis as a function of time **better explained as a Triangular Wave ACTUAL glottal volume velocity: o Speed and completeness of vocal fold closure affect roll-off. o In general, the low frequency harmonics dominate. Acoustic Theory of Speech Production Vocal tract acts as a filter o is frequency dependent. o Certain frequencies of the source signal pass through the filter with greater amplitude than others. **Selected frequencies Characteristics resonances formants Vocal Tract Transfer Function: - Resonance characteristics of the vocal tract - Specifies the vowel - Example: Model the vocal tract like a uniform tube » “schwa” vowel Ə Rule: For a tube closed, at one end and open at the other, the natural resonant frequency = wavelength 4X the length of the tube. Tube Representation of Vocal Tract In the Model… Glottis: ((with adducted vocal folds)) o Air particles vibrate LEAST effectively o Minimum velocity o Maximum pressure o Node (meaning there’s minimum velocity + maximum pressure) Lips: ((separated for vowel production)) o Air particles vibrate MOST effectively. o Maximum velocity o Minimum pressure o Antinode Some differences… Vocal tract not a completely uniform cross-section Oral cavity meets pharynx at 90 degree angle » Doesn’t matter acoustically Standing Wave Patterns Rule: The vocal tract will resonate only at odd-numbered multiples of the lowest frequency. Each resonant pattern is a standing wave = FORMANT Vowels - Supraglottal cavities are shaped by articulators - Formant values correspond roughly to articulatory postures. (will change the circumference of the tube)