Sinusoidal vibrations of the air Pure tone

Acoustic phonetics Flashcards by Mathilde R

Simple (sound) waves

Sinusoidal vibrations of the air
Pure tone

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We do not hear oscillations, but …

Tone/musical note

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Amplitude

the degree of change in air pressure, distance from zero to peak
* Correlated with loudness

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Frequency

the number of vibrations per unit of time
* Usually measured in Hz, i.e. cycles per second
* frequency = 1/wavelength

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Frequency and amplitude have an ______ relationship

Inverse

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Complex Waves

combination of simple tones
- The amplitude of a complex tone at a given point in time is the sum of amplitudes of its components at that point

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Constructive interference

when two waves combine, for an end result that is higher in amplitude

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Destructive interference

when two waves cancel out

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Complex waves are perceived as having a single _____

Pitch
- F0 (fundamental frequency) determined by the period

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Higher overtones do not impact the pitch, only ______

Timber

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sound quality, aka timbre

Determined by higher overtones
- What makes the sound different across instruments

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Aperiodic Sounds

No repeating pattern of sound: technically no wavelength nor fundamental frequency
* Can be analyzed as having energy at multiple frequencies

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Continuous aperiodic sound

random fluctuations over time
* E.g. white noise, unvoiced fricative

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Transient aperiodic sound

Not continuing
* E.g. balloon pop, tap, burst

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Fourier Analysis

A mathematical technique for decomposing a function into its oscillatory components
* Switching from the time domain (waveform) to the frequency domain (spectra)

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X and y axes of a spectra

X : frequency (Hz)
Y : amplitude

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We need multiple spectra (technically infinite) to represent it

Speech

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Spectrograms

Made up of multiple spectra lined up next to each other

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Axes of a spectrogram

X : frequency (Hz)
Y : amplitude (dB)
Z : time (msec)
Amplitude represented as hue

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Source

component causing vibration in the air
- All sounds have a source (sound is vibration)

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Filter

component typically in the vocal tract altering the vibration, acoustic properties of the source
E.g.
* Amplifying certain frequencies
* Dampening other frequencies
- Filter is technically not required

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Source and filter are _______dependent/independent

Independent : how you vibrate vocal folds is independent of how you manipulate the properties of the sound in the vocal tract

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Different vowels are different only in regards to the ______source/filter

Filter

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Source of approximants

Vocal fold vibration

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Harmonics

Prominent frequencies resulting from source vibration rates

Filter of approximants

Shape of the vocal tract that modifies timber

Formants

Resonant frequencies of the oral tract determined by the filter

F1 is ______inversely/positively correlated with height

Inversely

F2 is correlated with ______

Backness

Harmonics are always ______ multiples of the frequency of the first harmonic

Integer

vowel quality corresponds to...

Timber

Resonance

All objects vibrate at a particular natural frequency : vibrations are determined by the shape of the filter * Actually, infinitely many resonant frequencies :sound waves echo inside the object and interfere constructively (goes back toward the source)

The resonant frequencies of a perfect tube are ... of the lowest resonant frequency

integer multiples * True for higher formants

The resonant frequency of a single tube is determined by the tube ______

Length

Longer tube = _____ resonant frequency

Lower ( Shorter tube = higher resonant frequency)

Standing Wave

When a wave at a given point in space increases in amplitude over time due to constructive interference

Resonance is the result of echoes within an object forming ...

a standing wave * Depends on size and shape of object

In an open-ended tube, a resonant frequency has a _____ at one end and an ___ ____ at the other

Node, Anti node

At a given formant, the portion of the wave that would fit in vocal tract is ...

Fn = (2n-1)c / 4L where n is the formant number

What happens if we increase n ?

Frequency will go up (numerator increases), expected because lower formants have lower frequencies

What happens if we increase L ?

Frequency will go down, why longer vocal tract = lower resonant frequency

What happens if we change c ?

- Can change with air pressure and temperature - Increasing the c increases the resonant frequency

All the waves have a node at the _____ and anti-node at the _____

Node : glottis Anti-node : lips

acoustic filter of vowels

Whole vocal tract, from glottis to lips

Formant frequencies and vowel differentiation only depend on the _____ of the vocal tract

Shape

Single tube model (a tube that has the same diameter for its whole length and is closed at the glottis and open at the lips) works for this vowel

[ə]

Multiple-tube Model

The vocal tract can be modelled as multiple tubes, i.e. one tube that varies in diameter

If there is a constriction at a velocity maximum (V) (antinode) n a resonant wave then, the frequency of that resonance will ______decrease/increase

Decrease

if there is a constriction at a point of maximum pressure (P) (node), then the frequency of the resonance will ______decrease/increase.

Increase

Constrictions at the back of the oral tract _____decrease/increase F1

Increase

Constrictions at the front of the oral tract ____decrease/increase F1

Decrease

F1 is associated with vowel _____ (inversely correlated)

Height

Constrictions at the tongue root and the hard palate _____decrease/increase F2

Increase

Constrictions at the lips and the soft palate ______decrease/increase F2

Decrease

For two-tube models, there is a ____ and _____ resonating cavity

Front and back

The shape and size of the tubes is determined by ...

the position of the tongue and the inherent ‘imperfections’ of the vocal tract

Node

point at which amplitude in wave stays fixed

Antinode

point at which amplitude oscillates the most

Rounding's impact on formants

Lowers all formants

Vocal tract length varies from roughly ____ to ____

12-20 cm

Harmonics are determined by...

vocal folds, source, f0 (NOT a formant)

Formants are determined by ...

Glottis/lips distance (vocal folds), nodes/antinodes alter frequency (F1, F2, F3)

PITCH

What we hear is a combination of ... and ...

harmonics and formants

[i] formants

F1 and F2 with the biggest gap (low F1 and very high F2 because front)

[ɑ] formants

F1 and F2 closest together

Manner of Articulation in the spectrogram vs waveform

- Fairly distinctive - Both in spectrogram and in waveform

Voicing in spectrogram vs waveform

- Voice bar in spectrogram - Pulses in waveform

Place of articulation in spectrogram vs waveform

- Usually hard to see in the consonant itself - Can be observed in the vowel transitions in the spectrogram

[s]

has a concentration of energy above 5000Hz

[ʃ] has a concentration of energy _____ 5000Hz

Below

[f] and [θ] have _____ energy spread out across many frequencies

Few

Voiced fricatives look like ....

Voiceless fricatives + voice bar

Consonants produced at different places of articulation induce different ______ patterns at the beginning and end of vowels

Formant

Labials

sharp decrease in F1 and F2 toward consonant

Dorsals

decrease in F1 and increase in F2 toward consonant Also, decrease in F3 (velar ‘pinch’)

Coronals

formant transitions roughly similar to [ɪ] - F2 ~2000 Hz - F1 ~400 Hz

Nasals in the Spectrogram

Nasal (stops) radically alter the shape of the vocal tract

The distance between the glottis and the nostrils is greater than between the glottis and the lips, which creates ____ formants for nasals

Lower

more soft tissue in the nasal cavity means...

- Lower amplitude - Frequencies more spread out

Antiformants

When the oral cavity vibrates during the articulation of nasal stops - The vibration is not heard - Takes away some of the energy from the signal

Antiformants in the spectrogram

- Dips in the spectrum caused by the vibration of a cavity - Dependent on place of articulation`

r has a low ___

[w] looks like __ in the spectrogram

/u/

[j] looks like ___ in the spectrogram

[i]