The relationship between spectral characteristics and perceived hypernasality in children

Abstract

The purpose of this study was to quantify perceived hypernasality in children. One-third octave spectra of the isolated vowel [i] were obtained from 32 children with cleft palate and 5 children without cleft palate. Four experienced listeners rated the severity of hypernasality of the 37 speech samples using a 6-point equal-appearing interval scale. When the average 1/3-octave spectra from the hypernasal group and the normal resonance group were compared, spectral characteristics of hypernasality were identified as increased amplitudes between F1 and F2 and decreased amplitudes in the region of F2. Based on the findings of the children's speech, 36 speech samples with manipulated spectral characteristics were used to minimize the influences of voice source characteristics on perceived hypernasality. Multiple regression analysis revealed a high correlation (R = 0.84) between the amplitudes of 1/3-octave bands (1 k, 1.6 k, and 2.5 kHz) and the perceptual ratings. Increased amplitudes of bands between F1 and F2 (1 k, 1.6 kHz) and decreased amplitude of the band of F2 (2.5 kHz) was associated with an increasing perceived hypernasality. These results suggest that the amplitudes of the three 1/3-octave bands are appropriate acoustic parameters to quantify hypernasality in the isolated vowel [i].

Modeling of oropharyngeal articulatory adaptation to compensate for the acoustic effects of nasalization

“…[36][37][38]41,42 In this study, we analyzed a number of synthetic nasal vowels and identified various acoustic characteristics of nasalization that were consistent with prior findings. As demonstrated by the examples in Fig.…”

“…The articulatory adjustment was derived using the simulated annealing algorithm by coordinating the articulatory parameters (i.e., ART) of the speaker-adaptive model when the velopharyngeal port remained open to match the acoustic features (i.e., F1, F2, F3) calculated from the transfer function of model with that of a target oral vowel with a closed velopharyngeal port. Although the acoustic cues of nasalization are much beyond the three lowest formant frequencies, [36][37][38] incorporating these additional acoustic cues into the articulatory adjustment process largely increased the computation time. Due to the exploratory nature of this study, we only considered the three lowest formant frequencies, which can be computed in an efficient manner based on the transfer functions.…”

“…This apparent simplification of the acoustic representation of vowel nasalization improved computational efficiency but, as a trade-off, other acoustic cues of nasalization apart from the shifting of formant frequencies were not taken into account during inverse mapping. These acoustic cues, including reduction of formant amplitudes, increase of nasal resonances, and change of spectral balance across low-and high-frequency components, [36][37][38] need to be quantified and included in the cost function of inverse mapping in the improved model. Meanwhile, to accommodate the additional computational cost related to the computation of these acoustic cues, more efficient algorithms than the SAA need to be developed accordingly.…”

Acoustic analysis of voice in children with cleft palate and velopharyngeal insufficiency

“…Frequency instability, high intensity, abnormal formant distribution and abnormal spectrograms have been reported [10][11][12]. In 1989, Zajac and Linvile [11] studied voice perturbations in patients with VPI.…”

Spectral Analysis of Hypernasality in Cleft Palate Children: A PrePost Surgery Comparison

“…They were instructed to indicate the degree of perceived nasality in the speech samples based on the 6-point scale, where grade 0 representing "no nasal resonance" and 1, 2, 3, 4 and 5 representing "mild," "mild-moderate," "moderate," "moderately severe," and "severe hypernasal resonance" respectively. Earlier studies used similar scale to rate hypernasality [6,12]. They were further instructed not to pay attention to any other parameter of speech (voice, articulation, prosody etc) while they were doing the rating.…”