Exam 1 for comd 5070
3D spectrogram features (what are the three dimensions?) - correct answer-• X-axis- time;
y-axis- frequency
• Darkness on spectrogram indicates intensity (which would be high peaks in the spectrum)
• Y axis is limited to Nyquist (can't adjust upward beyond Nyquist, but can adjust downward)
• Wide band (ex: 300 hz)- gives clear time detail/ frequency resolution is poor (vertical
striations are glottal pulses)
Narrow band (ex: 45 hz)- gives clear frequency detail/ time resolution is poor (horizontal
striations are harmonics)
Aperiodicity - correct answer-• Sign wave- single line on spectrum
• Complex periodic signals- multiple lines
• Noise- many frequencies, equal amplitude, random phase
Voice- nearly periodic (no pure lines, has peaks, has some spread of energy around the
fundamental and harmonics)
Difference limens for frequency and intensity (what they are, how they are influenced by
frequency and intensity) - correct answer-• Frequency difference limens- smallest change in
frequency that a person can perceive
• Higher frequency sounds must differ more to be heard as different in pitch (low frequencies
show a more obvious difference than high frequencies)
As intensity decreases, difference limens become larger (soft sounds make it more difficult to
tell sounds apart in pitch)
Digital vs. analog signals (what makes a digital signal different from analog?) - correct
answer-• Digital- numeric (binary 0, 1)
o what is stored
o ex: clock with numbers only (no hands)
o discrete in time and amplitude
o Unknowns between points
o Like series of snapshots over time
o Computers only deal with binary data (computers are digital devices)
• Analog- analogy
o what is played back/heard
o continuous in time and continuous in amplitude
o ex: watch with hands
o Microphone to wire = analog representation of waveform collected
o Microphones/speakers are analog devices
• Analog to digital conversion (ADC)- microphone to computer
Digital to analog conversion (DAC)- computer to speakers
Electroglottograph (EGG) signal features (where does the signal come from? What does it
represent?) - correct answer-• Electrodes placed on both sides of the larynx (over thyroid
laminae) on surface of the neck, current is passed through from one side to the other
• Waveform represents movement of vocal folds
, • Stronger signal if vocal folds are closed, less current if vocal folds are separated
• Measures vocal fold contact area as vocal folds are opening and closing (changes in vocal
fold contact)
• EGG signal is revealing of features of the vocal source (shows only fundamental
frequency)
Does not measure sound pressure, glottal width, or opening/closing
Filter types (what do high or low pass or band pass or band reject filters do?) - correct
answer-• High pass- allows high frequencies through (removes/attenuates lower
frequencies)
• Low pass- allows low frequencies through (removes/attenuates lower frequencies)
• Band pass- allows a band of middle frequencies through (removes/attenuates high and low
frequencies)
Band reject- allows high and low frequencies through (removes/attenuates band of middle
frequencies)
Fourier transforms/analysis (what is the result of a Fourier transform of a sound? What does
it reveal about a complex sound?) - correct answer-• All periodic sounds are made of a
combination of sign waves (amplitudes, phase angles, frequencies vary)
• Reveals that complex sounds can be broken down into original sinusoid components
Fourier transform- take time domain waveform and creates a spectrum (to analyze its
frequencies)
Harmonic and inharmonic series (how do their ingredients differ? How and why do they
sound different?) - correct answer-• Harmonic series- multiples of the fundamental frequency
• Human voice- nearly periodic (has fundamental frequency and harmonic frequencies)
Inharmonic series- no mathematical relationships with the tones
How duration affects the loudness of brief sounds - correct answer-• Short sounds/ below
500 milliseconds affect perception (especially 15-150 ms)
Longer sounds seem more audible/louder (ear integrates energy)
How is loud speech different from conversational speech? - correct answer-Loud speech
requires in increase in subglottic pressure
How waveforms differ as frequency goes up or down - correct answer-• High frequency-
waves close together
• Low frequency- waves farther apart
Imagining the voice- high speed vs. stroboscopy (which is more for research and which is
clinical? How does each one work conceptually?) - correct answer-• High speed- 4000-6000
frames/second to make vocal fold vibrations look like smooth and slow movement, meant for
research/ not clinically practical because its expensive and too complex
• Stroboscopy- series of flash illuminated images of the vocal folds to make successive still
images played back in rapid succession which give illusion of motion (optical illusion), meant
for clinical practice
o Frozen image- flash occurs at same time in each cycle
Slow motion image- flashes occur slightly delayed in successive cycles
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