Comparison of spectral tilt measures for sentence prominence in speech—Effects of dimensionality and adverse noise conditions

Abstract

Linguistic prominence in speech is known to correlate with the acoustic measures of energy, F0, and duration. In contrast, the role of spectral tilt in the realization of prominence has remained more inconsistent between previous empirical investigations. This may be partially due to the lack of a standard method for quantifying spectral tilt or due to difficulties in estimating the acoustical source of spectral tilt, the glottal flow, from continuous speech. These issues have rendered interpretations and comparisons between studies difficult. In addition, (i) little is known about the robustness of tilt estimators for prominence detection in the case when speech is not clean but corrupted, as in real life, by environmental noise or telephone transmission (i.e. degradation caused by bandpass filtering and quantization noise). Moreover, (ii) little attention has been paid to multidimensional representations of source spectrum that can potentially incorporate more information about the phonation style than purely scalar measures. In this work, we study spectral tilt in signaling prominence in spoken Dutch and French under different levels of additive noise, and for telephoneband coded speech, and compare several one-dimensional tilt measures that have been previously encountered in the literature as well as multidimensional tilt measures. We also compare spectral tilt measures with other standard acoustic correlates for prominence, namely, energy, F0, and duration.Our results provide further empirical support for the finding that tilt is a systematic correlate of prominence in Dutch, that the role is smaller in French, and that energy, F0, and duration appear still to be the most robust features for discriminating prominent and non-prominent words. In addition, our results show that there are notable differences between different tilt measures at different levels of noise, and that multidimensional representations for tilt improve class separability from the scalar measures.

Acoustic voice characteristics with and without wearing a facemask

“…We also evaluated the low/high energy ratio (reflecting spectral slope) which is a ratio of spectral energy levels between the low and high frequency ranges to investigate how this would be affected given the impact of mask-wearing on the speech spectrum. The low/high ratio using a 1000 Hz cut-off value (LH1000) has been used frequently in voice and speech research and has been shown to reflect voice quality 62,63 , vocal load 64 , sentence prominence in speech 66 , and the effects of language 67 . The low/high energy ratio between spectral areas below 1 Hz and between 1-8 kHz was measured for the /a/ vowel (averaged from three repeats) and RP23 using the long-term average spectra (LTAS) function in Praat.…”

Vocal plasticity in harbour seal pups

“…In [ 16 , 59 ], speech in noisy conditions showed as a spectral energy boost between 0.5–1 kHz and 5 kHz when compared with the silent condition. There is high variance between different ways of measuring spectral tilt [ 60 ]; thus, here, spectral tilt was estimated using two separate methods.…”

Vocal plasticity in harbour seal pups

“…In [17, 75] speech in noisy conditions showed as a spectral energy boost between 0.5–1 kHz and 5 kHz when compared to the silent condition. Different ways to measure spectral tilt show high variance [76], thus, in the current study, spectral tilt was estimated using two separate methods.…”