Acoustic phonetics Flashcards
The frequency of air vibration is ______
Pitch
Simple (sound) waves
- Sinusoidal vibrations of the air
- Pure tone
We do not hear oscillations, but …
Tone/musical note
Amplitude
the degree of change in air pressure, distance from zero to peak
* Correlated with loudness
Frequency
the number of vibrations per unit of time
* Usually measured in Hz, i.e. cycles per second
* frequency = 1/wavelength
Frequency and amplitude have an ______ relationship
Inverse
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
How to combine sine waves into a square wave ?
Start with high amplitude, low frequency, and then add a wave that has lower amplitude but higher frequency.
Constructive interference
when two waves combine, for an end result that is higher in amplitude
Destructive interference
when two waves cancel out
Complex waves are perceived as having a single _____
Pitch
- F0 (fundamental frequency) determined by the period
Higher overtones do not impact the pitch, only ______
Timber
sound quality, aka timbre
Determined by higher overtones
- What makes the sound different across instruments
Aperiodic Sounds
No repeating pattern of sound: technically no wavelength nor fundamental frequency
* Can be analyzed as having energy at multiple frequencies
Continuous aperiodic sound
random fluctuations over time
* E.g. white noise, unvoiced fricative
Transient aperiodic sound
Not continuing
* E.g. balloon pop, tap, burst
Fourier Analysis
A mathematical technique for decomposing a function into its oscillatory components
* Switching from the time domain (waveform) to the frequency domain (spectra)
X and y axes of a spectra
X : frequency (Hz)
Y : amplitude
We need multiple spectra (technically infinite) to represent it
Speech
Spectrograms
Made up of multiple spectra lined up next to each other
Axes of a spectrogram
X : frequency (Hz)
Y : amplitude (dB)
Z : time (msec)
Amplitude represented as hue
Source
component causing vibration in the air
- All sounds have a source (sound is vibration)
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
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
Different vowels are different only in regards to the ______source/filter
Filter
Source of approximants
Vocal fold vibration
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
f0
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 ___
F3
[w] looks like __ in the spectrogram
/u/
[j] looks like ___ in the spectrogram
[i]
