Morphological and acoustical analysis of the nasal and the paranasal cavities

Abstract

Morphological measurements of the nasal and paranasal cavities were conducted to investigate their relevance to the acoustic properties of the human nasal tract. The magnetic resonance imaging (MRI) technique was used to measure the three-dimensional geometry of the vocal tract. The area function of the nasal tract was calculated for seven subjects based on data obtained during natural breathing. The entire vocal tract was measured for five subjects during sustained production of nasal consonants. A marked morphological difference was observed between our data and previously published data [A. S. House and K. N. Stevens, J. Speech Hear. Disord. 21, 218-232 (1956); G. Fant, Acoustic Theory of Speech Production (Mouton, The Hague, 1970), 2nd ed., p. 139] particularly in the middle portion of the nasal tract. Previous data derived from cadaver specimens showed a large cavity in the middle portion possibly due to an absent or dehydrated mucous membrane, while our data showed narrow passages due to thickly layered mucosa. It has been confirmed by an additional experiment that the wide cavity is reproducible by applying an adrenergic agent to the nasal mucosa. Transfer functions of the vocal tract and the nasal tract were calculated from measured data, and compared to spectra of real speech signals recorded subsequent to the MRI experiment. The results indicate that asymmetry between the two nasal passages can cause extra pole-zero pairs, and suggest that the paranasal cavities play an important role in shaping the spectral characteristics of human nasal sounds.

Mammalian laryngseal air sacs add variability to the vocal tract impedance: Physical and computational modeling

“…6͑b͔͒. The 5 cm long tube-SB introduced a pole/zero pair in the midfrequency range ͑1.5-4.0 kHz, the exact position depends on whether the side branch is open or closed or on the length or the inner diameter of the side branch͒ ͑Dang and Honda, 1997;Dang et al, 1994 As a consequence, all neighboring formants were shifted somewhat, where the first formant was most strongly shifted up to 25% ͓Figs. 6͑c͒ and 6͑d͔͒.…”

Comparison of magnetic resonance imaging-based vocal tract area functions obtained from the same speaker in 1994 and 2002

“…Since the early 1990's magnetic resonance imaging (MRI) has been used extensively to acquire volumetric image sets of the head and neck from which area functions can be directly measured (e.g., Lakshminarayanan, Lee, and McCutcheon, 1991;Baer, Gore, Gracco, and Nye, 1991;Yang and Kasuya, 1994;Dang, Honda, and Suzuki, 1994;Dang and Honda, 1997;Hoffman, 1996, andHaker, 1995, 1997;Narayanan, Alwan, and Song, 1997;Story, 2005b). These area functions are typically obtained for static vocal tract shapes and are assumed to be representative of a particular speaker's "normal" production of specific vowels or consonants.…”

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

“…For example, sagittal stacks were used by Narayanan et al (1997); Takemoto et al (2006), coronal slices used by Dang et al (1994), and axial slices used by Story et al (1996). However, due to constraints (time, money, and subject endurance) in MRI scanning, each image stack typically has an in-plane resolution which is much better than the out-of-plane resolution.…”