Laterals/ Fricatives

Question 1

What are the salient acoustic features of laterals

Answer 1

Shunt resonance in Laterals

Oral cavity shape: Single oral space posterior to constriction and two parallel later tracts anterior to constrictions

Posterior oral space produces antiresonances (1800hz-2000hz)

Shunt Resonance in Obstruents includes fricatives, stops and affricates.

For now constriction for non labials divides oral cavity and sound produced at point of constriction travels forward and backwards

Posterior oral cavity is like an enclosed space and produces an antiresonance (shunt resonator

Question 2

What properties differentiate the strident fricatives

Answer 2

Produces turbulent air flow
Primarily by amplitude (dB SPL)

Stridents are strident(loud) while non stridents are not as loud and much quieter

With Stridents (/s/and ʃ) there is primarily central tendency (peak frequency)
ʃ) peaks around 2.5-3.5 kHz

/S/ peaks around 4-6kHz ( These are for adults given that children peaks are higher

Question 3

What properties differentiate the strident fricatives

Answer 3

Within non-stridents (/f/ and /ɵ/): There is really no good acoustic cue for differentiating them

Question 4

What acoustic properties differentiate /s/ from /ʃ/?

Answer 4

Between (/s/and ʃ) both sounds are highly similar but peak frequencies are not very distinct from one another

Question 5

Describe the source filter theory

Answer 5

Vocal folds produce many source frequencies simultaneously (F0, all even and odd harmonics)

These are applied to a system or filter - the vocal tract
From among the source frequencies( vocal fold fundamental, harmonics and partials), those source frequencies that are close or equal to vocal tract’s natural frequencies will resonate( get amplified)

Those vocal fold frequencies far from vocal tract’s natural frequencies of vibration will be damped down

Thus, the vocal tract filters out those vocal fold source frequencies that are very different from its own natural frequencies of vibrations

Question 6

How do the natural resonant frequencies in strings depend on string length and speed of sound in strings

Answer 6

The string acts as a sound source like the vocal folds. The natural frequencies of vibration of the string (the source) provide the driving frequencies for the tube called( the filter)

The tube(filter) gets driven by the source like the vocal tract

The mass of air in the tube will simultaneously vibrate at all of the driving frequencies coming from the string however
Those driving frequencies from the string that are close to the natural frequencies of the tube will get amplified

The driving frequencies from the string that are far from the natural frequencies of the tube will get suppressed by the tube
This is a good model for the vocal tract

Question 7

Describe the Resonances in tubes and strings

Answer 7

String tied at both ends which is a good model for vocal folds. Note pattern of natural frequencies of vibration which are fundamental with both even and odd harmonics
Tube open-closed : Good model for the vocal tract and fundamental frequency plus only the odd harmonics
fn=n/c2L where n= 1,2,3
Resonances in Tubes: Deriving resonant frequencies formulas
Constraints : pressure node at open end and pressure antinode at closed end

The schwa vowel is unique and has relatively unconstricted vocal tract so an open- closed tube is a good model