Studied by 6 people
What is the source sound created through?
vocal fold vibration
If vocal folds are tighter the vibration and pitch is what?
vibration is faster and pitch is higher
Myoelastic aerodynamic theory of vocal fold vibration…
vf adduction through muscular contraction
build up subglottal (aka tracheal) pressure
when Ps is higher than Patm (pressure differential) and the Ps exceeds the glottal resistance, then
vfs will be blown apart air flows through the folds and will be proportional to driving pressure, then
vfs will recoil to midline and be sucked toward the midline by the Bernoulli effect
cycle starts over at 2. (no muscular contraction)
Air flow through glottis as a function of time
area
airflow
pressure
Area
area proportional to width of glotis/distance between vfs
Air flow
air flow proportional to width of glottis/distance between vfs
Pressure
pressure high/flow low
What is the nature of the signal generated by the vibrating vfs?
glottal airflow is proportional to glottal area
glottal airflow can be obtained by inverse filtering of the acoustic signal while glottal area is difficult to obtain.
glottal air flow is _____ to glottal area
proportional
How can glottal airflow be obtained?
by inverse filtering of the acoustic signal while glottal area is difficult to obtain
What would a fourier analysis of airflow signal yield?
A fourier analysis of airflow signal would yield a glottal source spectrum
f0=H1
roll off = -12dB
The waveform of glottal airflow repeats over time is equal to
periodic
If the period of the glottal airflow waveform is known what can be calculated?
F0 can be calculated
Low F0 >
harmonic more dense
High F0 >
harmonics less dense
If the period of a glottal waveform is 4 ms, what is the F0?
250 Hz
Since the glottal waveform is derived from the vibratory pattern of the vocal folds, what happens to the period?
the period of each successive cycle is not exactly the same
How do we refer to the signal created by vocal fold vibration?
quasiperiodic
What is the tilt?
steepness as determine by roll off
What does the tilt of the glottal spectrum give us info about?
the vibratory pattern of the vocal folds
When the glottal airflow is 0 the vfs are____
closed
During a typical vibratory cycle the glottis is open approx. _____ of the cycle and closed approx. _______ of the cycle__
open 60%
closed 40%
If the vocal folds close more slowly, the time the glottis is open is ____ yielding a steep tilt of the glottal source spectrum
longer
If the vocal folds snap together quickly the time the vocal folds are apart is _____ yielding a shallow tilt of the glottal source spectrum
shorter
The steepness of the amplitude decline in the source spectrum is related to what?
how quickly the vfs recoil
What is hyper function?
the vfs are over performing due to rapid forceful closing > less tilt > too much energy in higher frequency
What is the result of a hyperfunction voice?
pressed strained voice
What is hypofunction?
the vfs are underperforming due to slow or incomplete closing of vocal folds > more tilt ? very little energy in higher frequencies
What is the result of a hypofunction voice?
breathy weak voice
What is dysphonia?
abnormal voice quality
Four different acoustic measure of vf function that are informative about voice pathologies…
fundamental frequency
jitter
shimmer
harmonic to noise ratio (HNR)
What is fundamental frequency in vfs?
acoustic correlate of vf vibratory cycles per second
What is mean f0 for boys ages 6-10?
226 Hz
What is the mean f0 for girls ages 6-10?
238 Hz
What is the mean f0 for males?
106 Hz
What is the mean f0 for females?
193 Hz
What does jitter measure?
measures the cycle to cycle variations in vocal periods (frequency)
Jitter is the acoustic correlate of erratic _____
vibratory patterns
Jitter clinically correlates with what?
clinically it correlates somewhat with perceived roughness, hoarseness, and overall severity of dysphonia
What does a typical human exhibit in jitter
jitter levels around 1% or less
What does shimmer measure?
measures the cycle to cycle variations in peak amplitude (amplitude)
What is the acoustic correlate of shimmer?
acoustic correlate of noisy, breathy voice, and overall severity of dysphonia
The reference values for shimmer?
shimmer tends to be higher if vocal fold pathology is present, such as for example vocal nodules
What does harmonic to noise ration compare?
compares the amplitude of the periodic portion to the amplitude of the aperiodic portion of the signal
The _____ the HNR the more noise exists in the voice
lower
What is the acoustic correlate of HNR?
acoustic correlate of breathiness and hoarseness
What is HNR in children?
2 to 2.5 dB
What is HNR in adults?
7 to 19 dB
What are sonorant sounds?
vowels, approximants, nasals
In order to model the resonance frequencies of sonorant sounds we assume what?
a tube model closed at one end and open at the other
What impacts resonance frequencies?
length of the tube, speed of sound, and the shaped of the tube
What does rounding do?
lengthens the vocal tract
what are the three kinds of filters?
high pass
low pass
band pass
What kind of filter creates a resonance?
bandpass filters
Formant frequencies are the _____ frequencies of the vocal tract
resonance
Acoustically the vocal tract can be represented as a system of _______ with the formant frequencies as center frequencies
band pass filters
In addition to the filter function, the acoustic output is also determined by what?
the lip radiation effect
What is the highest octave frequency?
4000 Hz
What does the lip radiation effect provide?
a +6 dB/per octave boost
The lip radiation effect provides a +6 dB/per octave boost because…
the air particle vibration is pressurized as they exit the narrow lip opening
The lip radiation effect is the strongest in…
upper frequencies
We use the source filter theory to predict what?
the formant frequencies for schwa-no major constrictions
Although the vocal tract is open for all vowels, different constrictions occur at different _____ locations of the vocal tract
locations
What is the vocal tract filter also known as
vocal tract transfer function
When does the vocal tract filter change?
changes when the position of the tongue within the vocal tract changes
The tube open at one end is now the ____
front cavity
The back cavity and the constricted area together form a _____
helmholtz resonator
The resonances of the back cavity (helmholtz resonator) can be calculated using the forula of a tube that ___ at _____ ends
closed at both
How can the resonances of a back cavity be calculated?
Fn= nc/2L
What is the equation to calculate the first formant of a Helmholtz resonator?
F1= (1x34000 cm/s)/2xL
If the length of a tube decreases, the resonance frequency ______
increases
If the length of the tube increases the resonance frequency _____
decreases
In a tube that is open at one end and closed at the other a sound wave traveling in this type of tube will bounce off the closed end and what?
Reflect
When a tube is open at one end and closed at the other sounds what at the open end because of an impedance difference?
sounds will reflect back
When the incident wave and its echoes (reflected wave) interact they produce what?
Standing wave
A different way to model the effect of constrictions at different locations along the vocal tract is what?
Perturbation theory
Perturbation theory looks at the ways in which ___ and ___ velocity change as result of constriction location
pressure and velocity
What does pressure =
movement
What does velocity =
fast or slow
When pressure is at its maximum the velocity is ____
zero
i.e. air molecules don’t move
When velocity is at its maximum air pressure is ____
zero
air molecules are free to move to their fullest potential
What do resonance frequencies depend on?
the length of the tube
If the tube is _____ at a place where either pressure or velocity are at a maximum or minimum the resonance frequency changes in predictable ways
narrower
Constriction at a pressure maximum raises what?
the frequency of the resonance (formant)
If constriction is at a pressure maximum (velocity=0) air molecules are what?
forced further away from their rest position
When air molecules are forced further away from their rest position because constriction is at a pressure maximum what increases and raises frequency?
it increases stiffness which in turn raises frequency
Constriction at a velocity maximum lowers what?
the frequency of the resonance
When air molecules encounter a constriction they speed up which lowers what?
resonance frequency
If the constriction occurs at a point that is neither pressure nor a velocity maximum the frequency increases or decreases depending on what?
velocity and pressure values at that point of constriction
In our tube model only ____ the of wave length yields the first resonance of the tube.
1/4
The unconstricted vocal tract serves as reference
F1= _____Hz
F2= _____ Hz
F3= _____Hz
500 Hz
1500 Hz
2500 Hz
The first formant has relatively low pressure, therefore, relatively ___ ____
high velocity > F1 lower than schwa
The second formant pressure maximum (zero velocity) > _____
F2 higher than schwa
Third formant relatively high pressure, therefore realtively low velocity > ____
slightly higher than schwa
What is the source in the source filter theory?
larynx
What is the filter in the source filter theory?
vocal tract
How do we classify vowels?
height
frontness/backness
lip rounding
Who derived general rules that relate the acoustic output of vowel production to articulatory parameters?
Steven and House (1963)
F1 is _____ correlated to tongue height
Negatively
the higher the tongue the lower the F1
F2 is _______ correlated with tongue advancement
positively
the more front the vowel, the higher the F2
Note
Flashcard