Technique for “tuning” vocal tract area functions based on acoustic sensitivity functions

An alternative and complete derivation of the vocal tract length sensitivity function, which is an equation for finding a change in formant frequency due to perturbation of the vocal tract length [Fant, Quarterly Progress and Status Rep. No. 4, Speech Transmission Laboratory, Kungliga Teknisha Hogskolan, Stockholm, 1975, pp. 1-14] is presented. It is based on the adiabatic invariance of the vocal tract as an acoustic resonator and on the radiation pressure on the wall and at the exit of the vocal tract. An algorithm for tuning the vocal tract shape to match the formant frequencies to target values, such as those of a recorded speech signal, which was proposed in Story [J. Acoust. Soc. Am. 119, 715-718 (2006)], is extended so that the vocal tract length can also be changed. Numerical simulation of this extended algorithm shows that it can successfully convert between the vocal tract shapes of a male and a female for each of five Japanese vowels.

“…Story 10 proposed an automated process for modifying the area function that uses the sensitivity functions as a guide to match the formant frequencies with the target frequencies.…”

Section: A Methodsmentioning

confidence: 99%

Vocal tract length perturbation and its application to male-female vocal tract shape conversion

Adachi¹,

Takemoto²,

Kitamura³

et al. 2007

“…The sensitivity functions of the formants are calculated as the difference between the kinetic energy and potential energy at the formant frequency as a function of distance starting from the glottis, divided by the total energy of kinetic and potential energies in the system ͑Fant and Pauli, 1974;Story, 2006͒. The relative change of the formant that corresponds to the change in the area function can be described as…”

Section: Sensitivity Functions For F1-f5mentioning

confidence: 99%

A magnetic resonance imaging-based articulatory and acoustic study of “retroflex” and “bunched” American English /r/

Zhou

Espy‐Wilson

Boyce

et al. 2008

122

108

Speakers of rhotic dialects of North American English show a range of different tongue configurations for /r/. These variants produce acoustic profiles that are indistinguishable for the first three formants [Delattre, P., and Freeman, D. C., (1968). "A dialect study of American English r's by x-ray motion picture," Linguistics 44, 28-69; Westbury, J. R. et al. (1998), "Differences among speakers in lingual articulation for American English /r/," Speech Commun. 26, 203-206]. It is puzzling why this should be so, given the very different vocal tract configurations involved. In this paper, two subjects whose productions of "retroflex" /r/ and "bunched" /r/ show similar patterns of F1-F3 but very different spacing between F4 and F5 are contrasted. Using finite element analysis and area functions based on magnetic resonance images of the vocal tract for sustained productions, the results of computer vocal tract models are compared to actual speech recordings. In particular, formant-cavity affiliations are explored using formant sensitivity functions and vocal tract simple-tube models. The difference in F4/F5 patterns between the subjects is confirmed for several additional subjects with retroflex and bunched vocal tract configurations. The results suggest that the F4/F5 differences between the variants can be largely explained by differences in whether the long cavity behind the palatal constriction acts as a half- or a quarter-wavelength resonator.

“…where DF n is the change of the nth formant F n , S n is the sensitivity function of F n (Story, 2006), and DA i is the change of the ith section area A i . Section 1 is the first section starting from the glottis, and N is the last section number at the lips.…”

Section: Vocal Tract Area Functions and The Corresponding Acoustic Rementioning

confidence: 99%

Improved vocal tract reconstruction and modeling using an image super-resolution technique

Woo

Stone

Prince

et al. 2013

Magnetic resonance imaging has been widely used in speech production research. Often only one image stack (sagittal, axial, or coronal) is used for vocal tract modeling. As a result, complementary information from other available stacks is not utilized. To overcome this, a recently developed super-resolution technique was applied to integrate three orthogonal low-resolution stacks into one isotropic volume. The results on vowels show that the super-resolution volume produces better vocal tract visualization than any of the low-resolution stacks. Its derived area functions generally produce formant predictions closer to the ground truth, particularly for those formants sensitive to area perturbations at constrictions.