Sonorant Acoustics + Place Transitions

November 18, 2014

We Are Here.• Course project report #4 is due!

• I have guidelines to hand out for both:

• Course project report #5

• Your final course project report

• We still need a volunteer for the palatography demo!

• Heads up: I will be out next Thursday (the 27th)

• Una will be giving a lecture on exemplar theory

• Also heads up: the final exam has been scheduled.

• Friday, December 12th, from 3:30 – 5:30 pm

• In this classroom!

• Lastly: Hannah P.’s mystery spectrogram is up!

Nasal Formants• The values of formant frequencies for nasal stops can be calculated according to the same formula that we used for to calculate formant frequencies for an open tube.

• fn = (2n - 1) * c

4L

• The simplest case: uvular nasal .

• The length of the tube is a combination of:

• distance from glottis to uvula (9 cm)

• distance from uvula to nares (12.5 cm)

• An average tube length (for adult males): 21.5 cm

The Math

12.5 cm

9 cm

fn = (2n - 1) * c

4L

L = 21.5 cm

c = 35000 cm/sec

F1 = 35000

86

= 407 Hz

F2 = 1221 Hz

F3 = 2035 Hz

The Real Thing• Check out Peter’s production of an uvular nasal in Praat.

• And also Dustin’s neutral vowel!

• Note: the higher formants are low in amplitude

• Some reasons why:

• Overall damping

• “Nostril-rounding” reduces intensity

• Resonance is lost in the side passages of the sinuses.

• Nasal stops with fronter places of articulation also have anti-formants.

Anti-Formants• For nasal stops, the occlusion in the mouth creates a side cavity.

• This side cavity resonates at particular frequencies.

• These resonances absorb acoustic energy in the system.

• They form anti-formants

Anti-Formant Math• Anti-formant resonances are based on the length of the vocal tract tube.

• For [m], this length is about 8 cm. 8 cm

• fn = (2n - 1) * c

4LL = 8 cm

AF1 = 35000 / 4*8 = 1094 Hz

AF2 = 3281 Hz

etc.

Spectral Signatures• In a spectrogram, acoustic energy lowers--or drops out completely--at the anti-formant frequencies.

anti-formants

Nasal Place Cues• At more posterior places of articulation, the “anti-resonating” tube is shorter.

• anti-formant frequencies will be higher.

• for [n], L = 5.5 cm

• AF1 = 1600 Hz

• AF2 = 4800 Hz

• for , L = 3.3 cm

• AF1 = 2650 Hz

• for , L = 2.3 cm

• AF1 = 3700 Hz

[m] vs. [n]

• Production of [meno], by a speaker of Tsonga

• Tsonga is spoken in South Africa and Mozambique

[m] [e] [n] [o]

AF1 (m)

AF1 (n)

Nasal Stop Acoustics: Summary

• Here’s the general pattern of what to look for in a spectrogram for nasals:

1. Periodic voicing.

2. Overall amplitude lower than in vowels.

3. Formants (resonance).

4. Formants have broad bandwidths.

5. Low frequency first formant.

6. Less space between formants.

7. Higher formants have low amplitude.

Perceiving Nasal Place• Nasal “murmurs” do not provide particularly strong cues to place of articulation.

• Can you identify the following as [m], [n] or ?

• Repp (1986) found that listeners can only distinguish between [n] and [m] 72% of the time.

• Transitions provide important place cues for nasals.

• Repp (1986): 95% of nasals identified correctly when presented with the first 10 msec of the following vowel.

• Can you identify these nasal + transition combos?

Nasalized Vowel Acoustics• Remember: vowels are often nasalized next to a nasal

stop.

• This can obscure formant transitions.

• The acoustics of nasalized vowels are very complex.

• They include:

1. Formants for oral tract.

2. Formants for nasal tract.

3. Anti-formants for nasal passageway.

• Plus:

• Larger bandwidths

• Lower overall amplitude

Chinantec• The Chinantec language contrasts two degrees of nasalization on vowels.

• Chinantec is spoken near Oaxaca, Mexico.

• Check out the X-ray video evidence….

Oral vs. Partly Nasal

• Note: extra formants + expanded bandwidth…

• Tends to smear all resonances together in the frequency dimension.

Partly vs. Wholly Nasal

!Xoo Oral and Nasal Vowels

Laterals• Laterals are produced by constricting the sides of the tongue towards the center of the mouth.

• Air may pass through the mouth on either both sides of the tongue…

• or on just one side of the tongue.

Lateral Palatography

Lateral Acoustics• The central constriction traps the flow of air in a “side branch” of the vocal tract.

• This side branch makes the acoustics of laterals similar to the acoustics of nasals.

• In particular: acoustic energy trapped in the side branch sets up “anti-formants”

• Also: some damping

• …but not as much as in nasals.

• Primary resonances of lateral approximants are the same as those of for vocal tract length of 17.5 cm

• 500 Hz, 1500 Hz, 2500 Hz...

• However, F1 is consistently low (300 - 400 Hz)

4 cm

17.5 cm

• Anti-formant arises from a side tube of length 4cm

• AF1 = 2125 Hz

Laterals in Reality• Check out the Mid-Waghi and Zulu laterals in Praat

Mid-Waghi: [alala]

Velarization of [l]• [l] often has low F2 in English because it is velarized

• = produced with the back of the tongue raised

• = “dark” [l]

• symbolized

• Perturbation Theory flashback:

• There is an anti-node for F2 in the velar region

• constrictions there lower F2

Dark vs. Clear /l/

[alala]

•/l/ often has low F2 in English because it is velarized.

[l] vs. [n]• Laterals are usually more intense than nasals

• less volume, less surface area = less damping

• break between vowels and laterals is less clear

[ ] [ n ]

[l] vs.• [l] and are primarily distinguished by F3

• much lower in

• Also: [l] usually has lower F2 in English

[ ] [ ]

Glides

• Each glide corresponds to a different high vowel.

Vowel Glide Place

[i] [j] palatal (front, unrounded)

[u] [w] labio-velar (back, rounded)

[y] labial-palatal (front, rounded)

velar (back, unrounded)

• Glides are vowel-like sonorants which are produced…

• with slightly more constriction than a vowel at the same place of articulation.

• Each glide’s acoustics will be similar to those of the vowel they correspond to.

Glide Acoustics• Glides look like high vowels, but…

• are shorter than vowels

• They also tend to lack “steady states”

• and exhibit rapid transitions into (or from) vowels

• hence: “glides”

• Also: lower in intensity

• especially in the higher formants

[j] vs. [i]

[w] vs. [u]

Vowel-Glide-Vowel

[iji] [uwu]

More Glides

[wi:] [ju:]

Transitions• When stops are released, they go through a transition phase in between the stop and the vowel.

• From stop to vowel:

1. Stop closure

2. Release burst

3. (glide-like) transition

4. “steady-state” vowel

• Vowel-to-stop works the same way, in reverse, except:

• Release burst (if any) comes after the stop closure.

Stop Components

• From Armenian: [bag]

closure voicing

vowel

formant transitions

another closure

stop release burst

Confusions• When the spectrogram was first invented…

• phoneticians figured out quite quickly how to identify vowels from their spectral characteristics…

• but they had a much harder time learning how to identify stops by their place of articulation.

• Eventually they realized:

• the formant transitions between vowels and stops provided a reliable cue to place of articulation.

• Why?