R.J.J.H. van Son

An acoustic description of consonant reduction

Abstract The acoustic consequences of the articulatory reduction of consonants remain largely unknown. Much more is known about acoustic vowel reduction. Whether the acoustical and perceptual consequences of articulatory consonant reduction are comparable in kind and extent to the consequences of vowel reduction is still an open question. In this study we compare acoustic data for 791 VCV realizations, containing 17 Dutch intervocalic consonants and 13 vowels, extracted from read speech from a single male speaker, to otherwise identical segments isolated from spontaneous speech. Five acoustic correlates of reduction were studied. Acoustic tracers of articulation were based on F 2 slope differences and locus equations. Speech effort was assessed by measuring duration, spectral balance, and the intervocalic sound energy difference of consonants. On a global level, it shows that consonants reduce acoustically like vowels on all investigated accounts when the speaking style becomes informal or syllables become unstressed. Methods that are sensitive to speech effort proved to be more reliable indicators of reduction than F 2 based measures. On a more detailed level there are differences related to the type of consonant. The acoustic results suggest that articulatory reduction will decrease the intelligibility of consonants and vowels in comparable ways.

Formant frequencies of Dutch vowels in a text, read at normal and fast rate

Speaking rate is thought to affect the spectral features of vowels. Target‐undershoot models of vowel production predict more spectral reduction and coarticulation of vowels in fast‐rate speech than in normal‐rate speech. To test this prediction, a meaningful Dutch text of about 850 words was read twice by an experienced newscaster, once at a normal speaking rate and once as fast as possible. All realizations of seven different vowels and some realizations of the schwa (/E/) were isolated. The first and second formant frequency values of all realizations were measured at five different points, each time by making cross sections at different points in the vowel realization. The different selections of these points are based on procedures used in literature, such as maximal F1 or mean formant value. No spectral vowel reduction was found that could be attributed to a faster speaking rate, neither was a change in coarticulation found. The only systematic effect was a higher F1 value in fast‐rate speech irresp...

Formant movements of Dutch vowels in a text, read at normal and fast rate

Speaking rate in general, and vowel duration more specifically, is thought to affect the dynamic structure of vowel formant tracks. To test this, a single, professional speaker read a long text at two different speaking rates, fast and normal. The present project investigated the extent to which the first and second formant tracks of eight Dutch vowels varied under the two different speaking rate conditions. A total of 549 pairs of vowel realizations from various contexts were selected for analysis. The formant track shape was assessed on a point-by-point basis, using 16 samples at the same relative positions in the vowels. Differences in speech rate only resulted in a uniform change in F1 frequency. Within each speaking rate, there was only evidence of a weak leveling off of the F1 tracks of the open vowels /a a/ with shorter durations. When considering sentence stress or vowel realizations from a more uniform, alveolar-vowel-alveolar context, these same conclusions were reached. These results indicate a much more active adaptation to speaking rate than implied by the target undershoot model.

Duration and spectral balance of intervocalic consonants: A case for efficient communication

Abstract The prosodic structure of speech and the redundancy of words can significantly strengthen or weaken segmental articulation. This paper investigates the acoustic effects of lexical stress, intra-word location, and predictability on sentence internal intervocalic consonants from accented words, using meaningful reading materials from 4157 sentences read by two American English speakers. Consonant duration and spectral balance in such reading materials show reduction in unstressed consonants and in consonants occurring later in the word (Initial vs. Medial vs. Final). Coronal consonants behaved distinctly, which was interpreted as a shift from full to flap or tap articulation in a subset of the phoneme realizations. This shift in articulation, and part of the consonant specific acoustic variation, could be linked to the frequency distribution of consonant classes over the investigated conditions. A higher frequency of occurrence of a consonant class in our corpus and a CELEX word-list was associated with shorter durations and differences in spectral balance that would increase the communicative efficiency of speech.

Acoustics and perception of dynamic vowel segments

Abstract Some 550 vowel segments have been excised from a text read by a Dutch speaker, both at normal rate and at fast rate. The duration of each segment is measured, as well as static and dynamic formant characteristics, such as midpoint formant frequencies, and descriptions of the formant tracks in terms of 16 equidistant points per segment, or Legendre polynomial functions. We examined these formant characteristics as a function of vowel duration, but found no indication for duration-dependent undershoot. Instead, this speaker showed very consistent consonant-specific coarticulatory behavior and adapted his speaking style to the speaking rate in order to reach the same midpoint formant frequencies. Various (parabolically stylized) formant tracks, at various durations, in isolation or in CVC contexts, were synthesized and presented to listeners for identification. Net shifts in vowel responses, compared to stationary stimuli, showed no indication of perceptual overshoot. A weighted averaging method with the greatest weight to formant frequencies in the final part of the vowel tokens, explained the results best.

Perisegmental speech improves consonant and vowel identification

Abstract In two papers, Nearey (1992, 1997) discusses the fact that theories on phoneme identification generally favor strong cues that are localized in the speech signal. He proposes an alternative view in which cues to phoneme identity are relatively weak and dispersed. In the present listening experiment, Dutch subjects identified speech tokens containing fragments of vowel and consonant realizations and their immediate neighbors, taken from connected read speech. Using a measure of listener confusion based on the perplexity of the confusion matrix, it is possible to quantify the amount of information extracted by the listeners from different parts of the speech signal. Around half the information needed for the identification task was extracted from only a short, 40–50 ms, speech fragment. Considerable amounts of additional information were extracted from parts of the signal at, and beyond, the conventional boundaries of the segment, here called perisegmental speech. Speech in front of the target segment improved identification more than speech following the target segment, even if this speech was actually not part of the target phoneme itself. Correct identification of pre-vocalic consonants correlated with the correct identification of the following vowel, and vice versa. The identification of post-vocalic consonants was not correlated with the identification of the vowel in front. It is concluded that human listeners extract an important fraction of the information needed to identify phonemes from outside the conventional segment boundaries. This supports the proposal of Nearey that extended, “weak” cues might play an important part in the identification of phonemes.

A Survey on Perceived Speaker Traits: Personality, Likability, Pathology and the First Challenge

The INTERSPEECH 2012 Speaker Trait Challenge aimed at a unified test-bed for perceived speaker traits – the first challenge of this kind: personality in the five OCEAN personality dimensions, likability of speakers, and intelligibility of pathologic speakers. In the present article, we give a brief overview of the state-of-the-art in these three fields of research and describe the three sub-challenges in terms of the challenge conditions, the baseline results provided by the organisers, and a new openSMILE feature set, which has been used for computing the baselines and which has been provided to the participants. Furthermore, we summarise the approaches and the results presented by the participants to show the various techniques that are currently applied to solve these classification tasks.

A note on the neglect of the Doppler effect in the modelling of traffic flow as a line of stationary point sources

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