Nasal Acoustics

December 7, 2011

For Starters• Production Exercise #4 is due.

• I’ll send out a link to the production exam, once Production Exercise #4 has been graded.

• Friday: (optional) review for the final exam

• Reminder--Final Exam info:

• Monday, December 12th, 3:30-5:30 pm

• Science B 148

• After today’s lecture: evaluations of instruction

Lateral Acoustics• Laterals have resonances like vowels…

Mid-Waghi: [alala]

• but are weaker in intensity.

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

• much lower in

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

[ ] [ ]

Dark vs. Clear /l/

[alala]

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

Velarization in English• Different dialects:

1. [l] is velarized only in syllable-final position.

2. [l] is velarized everywhere except before front vowels.

3. [l] is velarized everywhere

Velarization in English

• Note: velarization of [l] leads to low F1 and low F2.

• closely resembles [o].

• Leading to dialect Option 4:

• The [l] disappears and the velarization is left behind.

• The Columbus, Ohio “[o:]dies” station

• Coldplay (Devon accent):

The Remainders• There are a handful of approximants in the IPA which are not considered glides, because they don’t correspond to high vowel articulations.

• These approximants correspond to flaps at the same places of articulation.

• An alveolar lateral flap is also possible:

Taps and Flaps• There is a technical distinction made between taps and flaps.

• Tap:

• strictly up and down movement, with brief contact between articulators.

• Spanish: “expensive”

• Flap:

• brief contact during backwards or forwards movement of an active articulator.

• N.A. English: “ladder” or “latter”

• Note: Deadheaded Ed had edited it.

Tap and Trill Acoustics

[pero] ‘dog’

From Spanish:

‘but’

Full Circle• The labio-dental flap was just introduced into the IPA in 2005.

• Re-check out the labio-dental flap movie.

Nasal Acoustics• The acoustics of nasal stops are quite complex.

• 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. Low frequency first formant.

4. Higher formants have low intensity.

5. Formants have broad “bandwidths”.

• Let’s account for each of these acoustic characteristics in turn.

Decreased Overall Amplitude

[m] [m]

Damping• The decreased overall amplitude of nasals is due to several factors, including damping.

• Recall that resonance occurs when:

• a sound wave travels through an object

• that sound wave is reflected...

• ...and reinforced, on a periodic basis

• The periodic reinforcement sets up alternating patterns of high and low air pressure

• = a standing wave

Resonance in a closed tube

Damping, schematized• In a closed tube:

• With only one pressure pulse from the loudspeaker, the wave will eventually dampen and die out

• Why?

• The walls of the tube absorb some of the acoustic energy, with each reflection of the standing wave.

Damping Comparison• A heavily damped wave wil die out more quickly...

• Than a lightly damped wave:

Damping Factors• The amount of damping in a tube is a function of:

• The volume of the tube

• The surface area of the tube

• The material of which the tube is made

• More volume, more surface area = more damping

• Think about the resonant characteristics of:

• a Home Depot

• a post-modern restaurant

• a movie theater

• an anechoic chamber

An Anechoic Chamber

Inside Your Nose• In nasals, air flows through the nasal cavities.

• The resonating “filter” of nasal sounds therefore has:

• increased volume

• increased surface area

• increased damping• Damping decreases amplitude…

• And spreads energy across a wider range of frequencies.

• = increased bandwidth

Bandwidth in Spectrograms

The formants in nasals have increased bandwidth, in comparison to the formants in vowels.

F3 of [m] F3 of

[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 ]

Nasal Plosion• One last, random thing about nasals--

• It is possible to “release” an oral stop closure by opening up the velo-pharyngeal port.

• The release burst caused thereby is referred to as nasal plosion.

• Peter says hidden, sadden, sudden, leaden

• with nasal plosion

• without nasal plosion

• Nasal plosion occurs in “pre-stopped” nasals in Russian:

• [dno] “bottom” [dna] “of the day”

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?