Speech & Hearing Sciences 2

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

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build up subglottal (aka tracheal) pressure

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when Ps is higher than Patm (pressure differential) and the Ps exceeds the glottal resistance, then

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vfs will be blown apart air flows through the folds and will be proportional to driving pressure, then

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vfs will recoil to midline and be sucked toward the midline by the Bernoulli effect

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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

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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

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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

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i.e. air molecules don’t move

When velocity is at its maximum air pressure is ____

zero

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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

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the higher the tongue the lower the F1

F2 is _______ correlated with tongue advancement

positively

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the more front the vowel, the higher the F2