2. Voicing + Basic Acoustics October 14, 2015

3. Agenda Production Exercise #2 is due on Friday! No transcription exercise this Friday! Today, we’ll begin working on the basic principles of acoustics. Next time, we’ll move on to suprasegmentals Pitch, Tone, length, etc. The mid-term is on Friday of next week. I’ll post a list of topics/concepts to review over the weekend; We’ll discuss the mid-term more next Wednesday.

4. 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

5. 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

6. 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…

7. 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

8. Laryngeal Settings We now know of two basic laryngeal settings for any pulmonic egressive sound: 1.Vocal folds are adducted (brought together) Air from lungs makes vocal folds “trill” = voiced sounds 2.Vocal folds are abducted (held apart) Air passes through glottis unobstructed = voiceless sounds

9. 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?

10. P in F ad How is sound transmitted through the air? Recall our bilabial trill scenario: Acoustics: Basics

11. 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?

12. 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 initial rest position Check out some atomic bomb videos…

13. 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

14. 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

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

16. Pressure Level Meters Microphones Have diaphragms, which move back and forth with air pressure variations Pressure variations are converted into electrical voltage Ears Eardrums move back and forth with pressure variations Amplified by components of middle ear Eventually converted into neurochemical signals We experience fluctuations in air pressure as sound

17. Measuring Sound What if we set up a pressure level meter at one point in the wave? Time pressure level meter How would pressure change over time?

18. Waveforms A waveform plots amplitude on the y axis against time on the x axis.

19. Complex Waves When more than one sinewave gets combined, they form a complex wave. At any given time, each wave will have some amplitude value. A 1 (t 1 ) := Amplitude value of sinewave 1 at time 1 A 2 (t 1 ) := Amplitude value of sinewave 2 at time 1 The amplitude value of the complex wave is the sum of these values. A c (t 1 ) = A 1 (t 1 ) + A 2 (t 1 )

20. Complex Wave Example Take waveform 1: high amplitude low frequency Add waveform 2: low amplitude high frequency The sum is this complex waveform: + =

21. Linguistically Speaking In speech, the fundamental frequency of voiced sounds is based on the rate at which the vocal folds open and close. The wave set up by the vocal folds is a complex wave.

22. Complex Wave Visual Combination of 100 Hz and 300 Hz wave. Voicing sort of looks like this, but it’s even more complex:

23. Why Should You Care? The modulation of fundamental frequency in speech can have linguistic meaning. Tone Pitch Accent Stress Intonation Since this modulation can occur (relatively) independently of the stream of vowel and consonant segments in speech… these linguistic properties are often referred to as suprasegmentals.