Speech and Hearing Exam 2

What is sound?

Propagation of pressure waves in a medium (air, water, steel)

What is elasticity?

Opposes displacement

What is intertia?

Opposes acceleration

T/F: vibration = elasticity + inertia

True

Compression =

High pressure

Rarefaction =

low pressure

What are pressure waves?

Alternation compression and rarefaction regions

T/F: the wave moves, not the molecules- the molecules oscillate around the rest

True

T/F: the molecules move, not the waves

False

What are sine waves?

Simple harmonic motion, one frequency (building block of complex sounds)

What are the two types of complex waves?

periodic + aperiodic

T/F: sine waves are periodic and have a single frequency

True

What are periodic waves?

Combination of fundamental frequency and its harmonics

What are aperiodic waves?

no repetition (fricatives)

What is frequency?

Cycles per second = 1/period

What are Periods?

Time for one cycle = 1/frequency

What is amplitude?

Height of the wave --> intensity/ loudness

How to calculate wavelength?

speed of sound/ frequency

What is a waveform?

Amplitude (y) over time (x)

What is a spectrum?

Amplitude (y) across frequencies (x)

How is a spectrum calculated?

Select a shorter time window from a waveform (5-50 ms)

Apply the fourier transform

Plot the result as a spectrum

What is the Fourier transform?

Breaks a complex wave into its individual sine wave components

What does each sine wave contain?

A frequency

An amplitude

Sometimes a phase

How do you plot a spectrum?

X- axis: frequency (Hz)

Y- axis: amplitude (intensity/ energy)

What is the difference between waveform and spectrum?

Time vs. frequencies

What is a complex periodic wave>

Sum of multiple sine waves (harmonics of F0)

What is a complex aperiodic wave?

No repeating pattern (EX: fricatives)

What is resonance?

Natural frequency of vibration

What is the helmholtz resonator?

Single frequency system

What is an example of a Helmholtz resonator?

Vowel cavity

How does acoustic mass change the resonant frequency in a Helmholtz resonator?

If Ma increases, resonant frequency decreases

How can Ma be increased?

Lengthening the neck (more air molecules)

Decrease neck opening

What is Ca (acoustic compliance)?

Inverse (opposite) of stiffness

What happens if Ca increases in a Helmholtz resonator?

Resonant frequency decreases

How can Ca be increased?

Larger bowls increase in R, more room for displacement

What is l in Helmholtz resonator?

Length of neck

What is a in Helmholtz resonator?

radius of circular neck opening

What is R in Helmholtz resonator?

Radius of circular bowl

What is Ma in Helmholtz resonator?

Acoustic mass

What is Ca in Helmholtz resonator?

Acoustic compliance

What are tube resonators?

Infinite resonant frequencies

What are standing waves?

Vibrating air molecules produce the same pressure variation at the same location

Two waves of the same frequency interfere/combine

Pressure within the tube appears 'frozen'

What is an example of a standing wave?

Blowing into a bottle, guitar string vibrating

What is the resonant frequency of a half- open tube?

Quarter wavelength rule

What is the resonant frequency of a tube open on both ends?

Half wavelength rule

What is an example of a tube resonator?

Vocal tract

What is damping?

Energy loss --> broader bandwidth, 'muffled' sound

What factors create damping?

Friction

Absorption

Radiation

Gravity

What is the source filter theory?

Source: vibrating VFs --> complex periodic sound

Filter: vocal tract--> shapes sound via resonance (formants)

What is the source in SFT?

Input signal generated by vibrating VFs

How can we look at the source from SFT?

Measure glottal flow

Inverse filtering

Difficult because VFs are too deep in the body

How to achieve inverse filtering?

Glottal source signal + Vocal tract filter = speech signal

What does the source spectrum look like?

Lowest Frequency: fundamental frequency (F0), first harmonic

Other frequencies are whole- number multiples of F0

How do we change the source spectrum?

Differences in vibration change the tilt

Period (and F0 changed depend on age, sex, etc.

The steeper the closing slope, the less tilted the spectrum

What are the formants?

Resonance peaks, determined by tongue height, advancement, and lip rounding

F1 down =

tongue height up

F2 up =

Tongue forward

Lip rounding =

All formants down (especially f2)

What is the perturbation theory?

Constrictions raise/ lower formant frequencies depending on position

When do constrictions raise the resonant frequency?

Constriction located a pressure maximum

Increases stiffness of air molecules

Greater constriction = greater increase in resonant frequency

When do constrictions lower resonant frequency?

Constriction located at velocity maximum

Increase acoustic mass (inertia) of air molecules

Greater constriction = greater decrease in resonant frequency

What is the non- uniqueness problem?

same formant pattern DOES NOT EQUAL same articulatory position

[i] = ?

High F2, low F1

[a] =

High F1, low F2

[u] =

Both F1 and F2 low

Dipthongs ?

Two articulatory targets, visible formant transitions on spectrograms

What would velum open + oral closure =

Nasal murmur

T/F: nasal murmur and nasalization are the same thing

False

T/F: nasal murmur does not equal nasalization

True

What is a shunt resonator?

Velopharyngeal port is open coupling the pharyngeal-oral and nasal tract

What are the effects of a shunt resonator?

Sound energy hits acoustic 'dead end'

Sound energy becomes trapped

Produces antiresonances

What is an antiresonance?

Opposite of resonance- instead of amplifying a sound it traps it

How are antiresonances created?

Created at the mouth and sinus cavities

(~Helmholtz resonators for sinuses)

Characteristics of Nasal Sounds

Contains resonances (nasal cavity) + antiresonance (oral/sinus cavities)

F1 ~ 250-300 Hz for all

Characteristic of /l/

Lateral airflow --> antiresonance affects F3

What happens during /r/ production?

Distinct F3 drop

T/F: sibilants are high in energy

True

T/F: non- sibilants are high in energy

false

Characteristics of sibilants

High energy, narrow high- frequency peaks

Characteristics of non- sibilants?

Low energy, broad frequency range

Why do non- sibilants have low energy and broad frequency range?

Their energy is spread out across frequencies instead of being concentrated in one high-energy region

How can you tell the difference between voiced and voiceless fricatives?

Voiced have an additional low- frequency energy due to VF vibration

Larger front cavity size =

Lower spectral peak

Stops:

Complete closure --> burst release --> possible aspiration

Voiceless stops:

Longer closure, stronger bursts

For which stops is there possible aspiration?

Energy in mid- frequencies (1-4kHz) not low or high frequencies

Acoustic characteristics of a closure (silent) interval?

VT radiates little to no acoustic energy

Silent in voiceless stops

Weak periodic energy in voiced stops

Acoustic characteristics of a release (burst) interval?

The release (burst) interval is a quick, noisy explosion of sound energy created when the closure of a stop is released.

It's broadband, short, and shaped by where the constriction occurs in the mouth.

Frication interval:

turbulent airflow after the burst (30-50 ms)

Aspiration interval:

Turbulent noise at constriction at the glottis (10-30 ms), voiceless stops only

VOT:

Time between bursts & first voicing ~ 40-80 ms; voices < 20 ms

/p, b/:

low burst frequency (600-899Hz)

/t, d/:

High ( ~1800 Hz)

/k, g/:

Burst near F2

Affricates:

Stop + fricative sequence, longer frication (~60-80 ms)

What is sampling?

Picking pieces of waveform

What Hz is adequate for speech?

22kHz

What is quantization?

bit depth (12-16 bits typical)

What is on the X- axis of a spectrogram?

Time

What is on the Y-axis of a spectrogram?

Frequency