Speech Acoustics Flashcards
1
Q
Voiced sounds
A
- Voiced sounds: the vocal folds shut, air pressure build up behind them, folds forced open, air flows through, folds snap shut and the cycle begins again- for voiced sounds the airflow is periodically interrupted.
2
Q
Voiceless sounds
A
- Voiceless sounds: the vocal cords are open all the time, there is no periodic structure to the sounds produce- these are often noise like sounds.
3
Q
Where does air flow during speech production after the vocal cords
A
- Air flows up through the pharynx into the mouth and for nasal sounds where the soft palate is lowered, into the nasal cavity.
4
Q
Source filter model
A
- The simplist description of speech production is called the source filter model.
- For a voiced sound the periodic airflow from the larynx is the source and has a certain spectral content (for unvoiced sounds the source is the turbulence)
- This is then modified by the articulators.
5
Q
Period and frequency
A
- Period= time required to complete one cycle
- Equations: T= 1/f
- Thus frequency (f) and period (T) are related.
- It is an inverse relationship: the larger the period, the slower the cycle and the fewer the cycles per second.
6
Q
Complex periodic sounds
A
Complex periodic sounds have a repetition frequency (fundamental) and higher frequency’s components at multiples of the fundamental (harmonies)
7
Q
Spectrograms
A
- To view the changes in speech spectrum through time we use a spectrogram.
- This shows the acoustic energy at each frequency and time.
- The darker the display, the more energy is present at that frequency.
- Allows us to view the dynamic changes in the speech spectrum.
8
Q
Vowels on spectrograms
A
- Relatively long duration, usually voiced, higher energy sounds.
- Tend to be dominated by low frequency energy.
- Characterised acoustically by peaks in the spectrum- formants.
- Formants are produced as a result of the acoustic resonances in the vocal tract.
- Changes in shape of the vocal tract produce different formant frequencies- which characterise the different vowels.
- Formants abbreviated here as f1 f2 f3.
9
Q
Voice pitch on spectrograms
A
- For many periodic sounds, we hear a subjective quantity known as pitch.
- Generally, the shorter the periodicity in the waveform, the higher the perceived pitch and vice versa.
- Fundamental frequency (and hence voice pitch) varies between men, women and children.
- Voice pitch- intonation- is used to carry linguistic information.
10
Q
Vowel transitions
A
- Formants stay at the same frequency for a steady state vowel.
- This rarely happens in speech.
- Usually the formant frequencies are in a state of change from one sound to the next.
- Eg diphthongs.
11
Q
Context dependency
A
- When vowels follow or precede different consonants the vocal tract changes shape during part of the vowel
- ## The vocal tract has one shape for the consonant and then has to change shape for the vowel
12
Q
Fricatives
A
- Fricatives /s/ /f/ /ʃ/ and the voiced equivelant /z/ /v/ /ʒ/
13
Q
Acoustic of consonant contrasts- fricatives
A
- Aperiodic signal occurring as a result of turbulence at the constriction in the vocal tract.
- Frication extends from 1kHz upwards to as high as 8-10 kHz for /s/
- Frication has different intensities, frequency ranges and duration .
- Non silibants (f, θ,v,ð) are weaker than their silibant (s, ʃ, z, ʒ) counterparts
- Voiceless non silibants (f, θ) are the weakest sound of English
- /s/ and /z/ have energy between 4 and 8 kHz.
- /ʃ and ʒ/ have energy at lower frequencies
- /h/ is produced by aspiration turbulence rather than by fricative turbulence.
14
Q
Plosives
A
Plosives /p/ /b/ /t/ /k/ /g/
15
Q
Affricates
A
Affricates /tʃ/ dʒ/
