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Sonorant Acoustics

Sonorant Acoustics. March 22, 2013. For Starters. Let’s do a perception experiment!. 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.

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Sonorant Acoustics

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  1. Sonorant Acoustics March 22, 2013

  2. For Starters • Let’s do a perception experiment!

  3. 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

  4. 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 • 4L L = 8 cm AF1 = 35000 / 4*8 = 1094 Hz AF2 = 3281 Hz etc.

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

  6. 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

  7. [m] vs. [n] [m] [e] [n] [o] AF1 (n) AF1 (m) • Production of [meno], by a speaker of Tsonga • Tsonga is spoken in South Africa and Mozambique

  8. Nasal Stop Acoustics: Summary • Here’s the general pattern of what to look for in a spectrogram for nasals: • Periodic voicing. • Overall amplitude lower than in vowels. • Formants (resonance). • Formants have broad bandwidths. • Low frequency first formant. • Less space between formants. • Higher formants have low amplitude. • Anti-formants!

  9. 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?

  10. 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: • Formants for oral tract. • Formants for nasal tract. • Anti-formants for nasal passageway. • Plus: • Larger bandwidths • Lower overall amplitude

  11. Nasal Vowel Movie

  12. Chinantec • The Chinantec language contrasts two degrees of nasalization on vowels. • Chinantec is spoken near Oaxaca, Mexico. • Check out the X-ray video evidence….

  13. Oral vs. Partly Nasal • Note: extra formants + expanded bandwidth… • Tends to smear all resonances together in the frequency dimension.

  14. Partly vs. Wholly Nasal

  15. !Xoo Oral and Nasal Vowels

  16. 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.

  17. 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.

  18. 17.5 cm 4 cm • 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) • Anti-formant arises from a side tube of length  4cm • AF1 = 2125 Hz

  19. Laterals in Reality • Check out the Mid-Waghi and Zulu laterals in Praat Mid-Waghi: [alala]

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