14 - Acoustics 4 - Consonants (I)

Question 1

Name two of the four characteristics of stops (plosives) that we might see on a spectrogram or oscillogram

Answer 1

Stop gap
- silent period of minimal or virtually no acoustic energy 50-150 msec in duration (voiced about 30 ms shorter than voiceless)

Release burst
-brief sound lasting about 10 msec (<40 msec) with a rapid amplitude rise time that appears as a vertical spike

VOT & Aspiration

• voice onset time interval between the release burst and onset of voicing
• aspiration noise is usually present in voiceless stops (not voiced stops) and is due to laryngeal friction

Formant transitions

• usually about 50 msec in duration
• F1 transitions move from low to high frequency following F1 rule
• F2 transitions are variable, but have constant starting point (locus value)

Question 2

Which type of phoneme is characterized by a momentary blockage of sound through the vocal tract: fricatives, affricatives, stops, nasals, or glides & liquids?

Answer 2

Stops (plosives)

Question 3

What are the 3 places of articulation (in English) for stops, and give a phonemic example of each

Answer 3

Lips - p/b
Alveolar - t/d
Velar - k/g

Question 4

What are the 2 types of stops?

Answer 4

Voiced and voiceless

Question 5

Which has a longer stop gap: voiceless or voiced stops?

Answer 5

Voiceless (by about 30 msec)

Question 6

What is a stop gap?

Answer 6

A silent period of minimal or virtually no acoustic energy

• interval that corresponds to articulatory occlusion
• 50-150 msec in duration

Question 7

True or false: voiced stops may show a very low intensity voicing signal during the stop gap

Answer 7

True

Question 8

True or false: certain speech disorders will show ‘voicing throughout the stop gap’ of voiceless stops

Answer 8

True

Question 9

What is the ‘release burst’?

Answer 9

A very brief sound lasting about 10 msec (<40 msec), with a very rapid amplitude rise time that appears as a very brief vertical spike on the oscillogram and spectrogram
- caused by turbulent noise and high velocity (jet) of air as the stop occlusion is released

Question 10

The frequency spectrum of the release burst changes with place of articulation. Which of the following have the highest frequency peaks and which have the lowest:
lip (p-b)
alveolar (t-d)
velar (k-g)

Answer 10

Highest: alveolar (t-d)
Intermediate: velar (k-g)
Lowest: lips (p-b)

Question 11

What is the laryngeal devoicing gesture?

Answer 11

Actively opening up the vocal folds

- used with voiced stops

Question 12

What is the voice onset time (VOT)?

Answer 12

The time interval between the release burse and the onset of voicing (vocal fold vibration)
- VOT of voiceless stops is 25-100 msec

Question 13

In disordered speakers (ie. apraxia of speech), what happens to the VOT values for voiced and voiceless stops?

Answer 13

They can become quite variable and highly overlapping

Question 14

Is aspiration noise usually present in voiceless or voiced stops?

Answer 14

Voiceless - due to the laryngeal frication noise (turbulent noise) that results when the vocal folds start to approximate for voice onset

Question 15

What do formant transitions reflect in stops?

Answer 15

Formant transitions reflect the articulatory movement from the stop occlusion to the vowel configuration

• changes in vocal tract shape produce fairly predictable changes in vocal tract resonances (formants)
• usually about 50 msec in duration

Question 16

What do ‘locus’ values refer to?

Answer 16

Locus values refer to the relatively constant and predictable F2 starting point for each place of stop articulation
- the place on the frequency scale to which the F2 transitions point

Question 17

List the F2 locus frequencies for /b/, /d/, and /g/

Answer 17

/b/ = 800 Hz
/d/ = 1800 Hz
/g/ = 3000 Hz