Voicing + Basic Acoustics

1. Voicing + Basic Acoustics October 9, 2013

2. Agenda • Homeworks are due! • Friday: transcription exercise on airstream mechanisms • Amharic, Chichewa, N|uu • Which reminds me: Miriam Makeba video • Production Exercise #2 has also been posted. • due Monday the 21st • Today, we’ll begin working on the basic principles of acoustics. • On Monday, we’ll move on to suprasegmentals • Pitch, Tone, length, etc.

3. Voicing = Glottal Trills • Voicing occurs when: • air rushes up from the lungs • the vocal folds are brought together (adducted)

4. Creaky Voicing • The flow of air from the lungs forces the vocal folds to open and close. • The slowest type of voicing is called “creaky voice.”

5. Modal Voice • This is normal, or “modal” voicing. The rate of glottal trilling is considerably faster. • How fast do you think the vocal folds open and close in normal voicing?

6. Vocal Fold Specs • In bilabial trills, lips open and close 25 times a second • In modal voicing, the glottal trill cycle recurs, on average: • 120 times a second for men • 220 times a second for women • 300+ times a second for children

7. Vocal Fold Specs • Air rushes through vocal folds at 20 to 50 meters per second • Between 72 and 180 kph (45 ~ 120 mph) • Due to Bernoulli Effect, pressure between vocal folds when this occurs is very small • Speed of “glottal trill” cycle depends on: • thickness of vocal folds • tenseness of vocal folds • length of vocal folds

8. Vocal Fold Specs • In men, vocal folds are 17-23 millimeters long • In women, vocal folds are 12-17 millimeters long • Adult male vocal folds are 2-5 millimeters thick • Adult female vocal folds are slightly thinner • Thicker, longer folds vibrate more slowly • Think: violin strings vs. bass strings • Tenseness of vocal folds can be changed to alter the speed of glottal opening and closing. • Like tuning a violin or a guitar…

9. Terminology • Frequency is the rate at which vocal folds are opening and closing • measured in Hertz (cycles per second) • Period is the length of time between cycles • Frequency = 1 / Period • Pitch is the perception of frequency • Lower frequency = lower perceived pitch • Higher frequency = higher perceived pitch

10. Laryngeal Settings • We now know of two basic laryngeal settings for any pulmonic egressive sound: • Vocal folds are adducted (brought together) • Air from lungs makes vocal folds “trill” • = voiced sounds • Vocal folds are abducted (held apart) • Air passes through glottis unobstructed • = voiceless sounds

11. Independence • Stops can be voiced or voiceless. • Two anatomically independent settings: • Place of articulation • Voiced/Voiceless • Are these two settings aerodynamically independent of each other? • Is it easier to make a voiced or a voiceless stop?

12. Cross-linguistic Data • From Ruhlen (1976), who surveyed 706 languages • 75% had both voiced and voiceless stops • Of the remaining 25%... • 24.5% had only voiceless stops • 0.5% had only voiced stops •  voiced stops are hard

13. One step further • Are some voiced stops harder than others? • Stop inventories: • English p t k • b d g • Thai p t k • b d • Efik t k • b d

14. More Cross-Language Data • From Sherman (1975), who surveyed the stop inventories of 87 languages. • 2 languages were missing voiced bilabials • 21 languages were missing voiced dentals/alveolars • 40 languages were missing voiced velars •  voiced velars are particularly hard • Why?

15. Place and Volume:a schematic pharynx mouth lips glottis

16. Place and Volume:a schematic • Voicing occurs when air flows through the glottis airflow glottis

17. Place and Volume:a schematic • For air to flow across the glottis… • the air pressure below the glottis must be higher than the air pressure above the glottis • Pbelow > Pabove Pabove Pbelow glottis

18. Place and Volume:a schematic stop closure • If there is a stop closure and… • Air is flowing through the glottis… • The air above the glottis will have nowhere to go Pabove Pbelow glottis

19. Place and Volume:a schematic stop closure Air pressure below the glottis will drop Air pressure above the glottis will rise The difference between the two will decrease Pabove Pbelow glottis

20. Place and Volume:a schematic stop closure • (Pbelow - Pabove)  0 • Airflow across the glottis will cease • Voicing will stop Pabove Pbelow glottis

21. Place and Volume:a schematic velar stop closure decreased volume • The further back a stop closure is made… • The less volume there is above the glottis for air to flow into Pabove Pbelow glottis

22. Place and Volume:a schematic velar stop closure decreased volume • Pabove will increase more rapidly as air flows through the glottis • Voicing will cease more quickly Pabove Pbelow glottis

23. More Numbers • From Catford (1982), Fundamental Problems in Phonetics • Lung volume = 1840 - 4470 cm3 • During inhalation/exhalation, lung volume typically changes 500-1000 cm3 • Vocal tract volume = space between glottis and oral closure: • Bilabials: 120-160 cm3 • Alveolars: 70-100 cm3 • Velars: 30-50 cm3

24. Morals of the Story • Voiced stops are hard because too much air gets pushed into the mouth, behind the stop closure • This makes it impossible for there to be a pressure drop across the glottis. • Voiced velars are worse, because the space above the glottis, behind the stop closure, is even smaller. • This space gets filled up by pulmonic airflow even faster • Independent articulatory gestures may interact aerodynamically • They have to share the same stream of air.

25. Some Leftovers • Velar trills? • Velars often have multiple release bursts… • due to the massiveness (and sluggishness) of the back of the tongue • Check out an example. • An alternate strategy to maintain voicing: • pre-nasalization • [mb], [nd], etc.

26. Implosive Stats • Implosives often begin life as voiced stops. • Trying to voice them completely can lead to them becoming implosives. • Implosives are more frequently found at fronter places of articulation • Bilabial: 39 Palatal: 7 • Alveolar: 36 Velar: 5 • Retroflex: 1 Uvular: 1 • The lack of more posterior implosives may be due to the lack of posterior voiced stops to begin with.

27. Acoustics: Basics • How is sound transmitted through the air? • Recall our bilabial trill scenario: Fad Pin Fad

28. What does sound look like? • Air consists of floating air molecules • Normally, the molecules are suspended and evenly spaced apart from each other • What happens when we push on one molecule?

29. What does sound look like? • The force knocks that molecule against its neighbor • The neighbor, in turn, gets knocked against its neighbor • The first molecule bounces back past its initial rest position Check out some atomic bomb videos… initial rest position

30. What does sound look like? • The initial force gets transferred on down the line rest position #1 rest position #2 • The first two molecules swing back to meet up with each other again, in between their initial rest positions • Think: bucket brigade

31. Compression Wave • A wave of force travels down the line of molecules • Ultimately: individual molecules vibrate back and forth, around an equilibrium point • The transfer of force sets up what is called a compression wave. • What gets “compressed” is the space between molecules

32. Compression Wave area of high pressure (compression) area of low pressure (rarefaction) • Compression waves consist of alternating areas of high and low pressure