Peri Bhaskararao

The trills of Toda

A hundred years from now a large number of presently spoken languages will no longer be viable means of communication, and the distinctive sounds that they contain will have disappeared. Of the nearly seven thousand languages in the world listed by Grimes (1992), about ten per cent are spoken by around a thousand people or less. As the speakers of these languages grow old, and their children go to schools in which the main languages of the country predominate, phoneticians will no longer have access to the wide variety of sounds currently in use. Toda, a language spoken by about a thousand speakers in the Nilgiri Hills of Southern India, has some unusual sounds that will probably not exist in our great grandchildrens times. Among them are the six trills which this paper will describe. Tongue tip trills occur in about one third of the worlds languages (Maddieson 1984). None of the languages in Maddiesons sample has two contrasting apical trills without secondary articulations, although they have been reported in Malayalam (Ladefoged 1971). To the best of our knowledge only Toda has three contrasting trills; and almost certainly no other language has surface contrasts between palatalized and non-palatalized versions of three lingual trills. Toda is a rich source for trill-seeking phoneticians.

Acoustic analysis of trill sounds

In this paper, the acoustic-phonetic characteristics of steady apical trills--trill sounds produced by the periodic vibration of the apex of the tongue--are studied. Signal processing methods, namely, zero-frequency filtering and zero-time liftering of speech signals, are used to analyze the excitation source and the resonance characteristics of the vocal tract system, respectively. Although it is natural to expect the effect of trilling on the resonances of the vocal tract system, it is interesting to note that trilling influences the glottal source of excitation as well. The excitation characteristics derived using zero-frequency filtering of speech signals are glottal epochs, strength of impulses at the glottal epochs, and instantaneous fundamental frequency of the glottal vibration. Analysis based on zero-time liftering of speech signals is used to study the dynamic resonance characteristics of vocal tract system during the production of trill sounds. Qualitative analysis of trill sounds in different vowel contexts, and the acoustic cues that may help spotting trills in continuous speech are discussed.

Two types of voiceless nasals

Many languages in South East Asia have voiceless nasal consonants that contrast with their voiced counterparts. What has not been reported previously is that there are two distinct types of voiceless nasals. We will begin by considering the more well-known type, found in languages such as Burmese. These voiceless nasals are usually said to have an open glottis for most of the articulation, but some voicing for the period just before the stricture is broken (Ladefoged 1971: 11). In this view they have two parts. The first is necessary to distinguish them from their voiced counterparts. The second distinguishes one voiceless nasal from another, by making the place of articulation more apparent; the voiced offglide from the nasal into the vowel has formant transitions that are characteristic of each place of articulation. Dantsuji has shown that, in addition, the voiced portion of the voiceless nasals in Burmese “includes significant cues which can distinguish points of articulation” (Dantsuji 1986: 10). Despite the small voiced portion, in most phonological treatments of these sounds, a voiceless nasal consonant is considered not as a sequence of two items, a voiceless segment followed by a voiced segment, but as a single voiceless unit with a low level phonetic rule inserting the voicing towards the end. Burmese is a textbook example, with forms as shown in Table 1 (from Maddieson 1984; also in Ladefoged 1993: 282).

Study of the effects of vocal tract constriction on glottal vibration

Characteristics of glottal vibration are affected by the obstruction to the flow of air through the vocal tract system. The obstruction to the airflow is determined by the nature, location, and extent of constriction in the vocal tract during production of voiced sounds. The effects of constriction on glottal vibration are examined for six different categories of speech sounds having varying degree of constriction. The effects are examined in terms of source and system features derived from the speech and electroglottograph signals. It is observed that a high degree of constriction causing obstruction to the flow of air results in large changes in these features, relative to the adjacent steady vowel regions, as in the case of apical trill and alveolar fricative sounds. These changes are insignificant when the obstruction to the airflow is less, as in the case of velar fricative and lateral approximant sounds. There are no changes in the excitation features when there is a free flow of air along the auxiliary tract, despite constriction in the vocal tract, as in the case of nasals. These studies show that effects of constriction can indeed be observed in the features of glottal vibration as well as vocal tract resonances.

Analysis of breathy voice based on excitation characteristics of speech production

The objective of this paper is to find the fundamental difference between breathy and modal voices based on differences in speech production as reflected in the signal. We propose signal processing methods for analyzing the phonation in breathy voice. These methods include technique of zero-frequency filtering, loudness measurement, computation of periodic to aperiodic energy ratio and extraction of formants and their amplitudes using group-delay based technique. Parameters derived using these methods capture the excitation source characteristics which play a prominent role in deciding the voice quality. Classification of vowels into breathy or modal voice is achieved with an accuracy of 93.93% using the loudness measure.

Use of triphones for demisyllable-based speech synthesis

The authors describe a novel speech synthesis unit, called a triphone, which is being incorporated into demisyllable-based synthesis systems for Hindi and English. The triphone unit consists of a vowel-consonant-vowel combination and is being used for synthesizing intervocalic consonants of short duration. Results show that the triphone is useful for the synthesis of certain intervocalic consonants which cannot be well modeled using the standard demisyllable approach.<<ETX>>

Differences among retroflex consonants

Both Dravidian languages such as Telugu and Indo‐Aryan languages such as Hindi have contrasts between dental and retroflex consonants. But what is called retroflex in Telugu is not the same as what is called retroflex in Hindi. X‐rays of five speakers of each of these languages producing minimal pairs exhibiting these contrasts show that the tongue tip is curled further up and back in the Telugu retroflex consonants than in those in Hindi. The dental consonants in the two languages are more similar. The articulatory differences are reflected in the acoustic data. As expected the formant transitions for the Telugu retroflex consonants involve a greater lowering of the third formant. These results appear to be contrary to the predictions of the quantal theory of speech production, which suggests that there should not be small but significant variations in the articulation of such consonants.