Effects of Phonetic and Inventory Constraints in the Spirantization of Intervocalic Voiced Stops: Comparing two Different Measurements of Energy Change.

Marta Ortega-LLebaria University of Northern Colorado E-mail: [email protected]

This paper extends the same hypothesis to the phenomenon ABSTRACT of spirantization by investigating the interaction of phonetic factors with inventory constraints. First, it This paper examines the effect of inventory constraints and examines whether the phonetic factors of stress and the phonetic factors of stress and vowel context in the context, which had an effect in the of Spanish lenition of English and Spanish intervocalic voiced stops. intervocalic /g/ [3], had also an effect in English Five native speakers of and five native intervocalic /g/ and in Spanish and English intervocalic /b/. speakers of Caribbean Spanish were recorded saying Secondly, this paper studies the interaction of inventory bi-syllabic words containing intervocalic /b/ and /g/. The constraints with phonetic factors. Inventory constraints intervocalic consonants were evaluated according to two were aimed to preserve the system of sound contrasts of a measures of energy, i.e. RMS ratio, and speed of consonant language while phonetic factors provided contexts that release. Repeated Measures ANOVAS in each measure favored consonant lenition. Hypothetically, a consonant indicated that for both languages, /b/ and /g/ were most will become lenited in a favorable context only if the lenited in trochee words, and that /g/ was most spirantized resulting sound will not impair a contrast of the language. when flanked by /i/ and /u/ . Inventory constraints For example, in English, /b/ contrasts with the voiced moderated the degree of consonant lenition displayed in the fricative /v/ while in Spanish, it does not. However, neither aforementioned favorable contexts by reducing the amount Spanish nor English /g/ contrast with a voiced velar of spirantization if the resulting sound impaired a contrast fricative sound. Consequently, in contexts favorable to of the language. lenition, the difference in the degree of lenition between Spanish and English /b/ will be greater than that between 1. INTRODUCTION Spanish and English /g/.

Lenition of intervocalic voiced stops is a process of 2. METHODOLOGY weakening or reduction of articulatory effort, which has been, analyzed as both a categorical and gradient 2.1 SUBJECTS phenomenon. For example, in Spanish, lenition of voiced stops has been interpreted as a case of where Ten female subjects participated in the study, 5 native the spirantized consonant acquired the [+continuant] speakers of Caribbean Spanish and 5 native speakers of feature from adjacent vowels [1,2]. However, recent studies American English. The ages of the subjects within each have described spirantization as a gradient phenomenon language group ranged from the mid twenties to the early conditioned by phonetic factors. Cole, Hualde and Iskarous fifties. From birth to adolescence, all participants had [3] found that the degree of spirantization of Spanish received extensive input primarily in their mother tongue to intervocalic /g/ varied according to stress and vowel communicate with parents and siblings. They first became contexts. This consonant became most spirantized in literate in their native language, and not until at least age 10 unstressed syllables flanked by /o/ and /u/ vowels, i.e. sugus, did any of them started learning a second language, nor had and least spirantized in stressed syllables flanked by /a/ lived in a country where a foreign language was spoken. vowel, i.e. amagar. Presently, all subjects make extensive use of their native language in their daily life. Other studies have related variability in speech production with inventory constraints. For example, Manuel [4] 2.2 MATERIALS AND TASK defined inventory constraints as inventory size, and demonstrated how they had predictive value with respect Subjects participated in a memory game in which they had how extensively various phonemes were coarticulated in to recall the names of 12 invented cartoon characters. Their particular languages. Languages with less crowded vocalic names, which were /bába/, /babá/, /bíbi/, /bibí/, /búbu/, inventories and more acoustic space for individual vowels /bubú/, /gága/, /gagá/, /gígi/, /gigí/, /gúgu/, /gugú/, related tolerated more coarticulation than those with more vowels to the physical appearance of the cartoon characters. For with less acoustic space. example, the vowels of the character’s name were color-coded: red equaled vowel /a/, green vowel /i/, and 81.05 79.44 blue vowel /u/. Each cartoon character was wearing a piece of clothing. Subjects’ task was to create a sentence in their native language that contained the name of the character and the piece of clothing it was wearing, i.e. “Mister Bubú is wearing a hat” or “El señor Bubú lleva un sombrero”. The objective of this task was to obtain utterances that 52.12 44.02 0 0.593968 0 0.515959 contained consonant lenition. Therefore, the task was Time (s) Time (s) designed as a game where participants felt comfortable to b ú b u b u b ú speak in an informal register [5]. Moreover, the memory load of the game distracted participants from focusing on Figure 2: Measure of Speed of Consonant Release in sound pronunciation. /búbu/ and /bubú/ words. The difference between the maximum and minimum intensity of the intervocalic 2.3 RECORDINGS AND MEASUREMENTS consonant as function of time measured speed of consonant Subjects were recorded in a sound attenuated room. Each release. Arrow signals the points of minimum and subject produced a sentence for each one of the 12 cartoon maximum intensity. characters. The same task was repeated four additional times. Recordings were made directly into a computer, 3. RESULTS which digitized sound at a sampling rate of 44 KHz and 16 bits of resolution. Repeated Measures ANOVA analyses were performed on the RMS ratio measurements and on the speed of consonant The intervocalic consonant in each target word, i.e., /bába/, release measurements. Each ANOVA contained the was evaluated according to two measures of energy. First, within-subject factors of consonant (b, g), vowel (a, i, u), the RMS ration of the intervocalic consonant to the VCV and stress (trochee, iamb), and the between-subject factor part of the word was measured. The closer this ratio came of language (Spanish, English). to 1, the more vowel-like was the consonant, while a ratio closer to 0 indicated that the intervocalic consonant was 3.1 EFFECTS OF STRESS produced with a stop closure. Results indicated that stress influenced the degree of spirantization of intervocalic stops. A significant main effect in RMS measures and in speed of consonant release 5000 5000 showed that speakers from both Spanish and English produced intervocalic consonants in trochee words, i.e. bába, with more lenition than those in iambic words, i.e. babá. Lenited consonants in trochees obtained higher RMS scores (Figure 3) and slower release motions than consonants in iambs. Moreover, Spanish consonants were spoken with a higher overall degree of lenition than their English counterparts, as indicated by the interaction stress*language. 0 0 0 0.593968 0 0.515959 Time (s) Time (s) 1.1 b ú b u b u b ú 1.0 Figure 1: RMS ratio measures in /búbu/ and /bubú/ words. .9 RMS ratio of the intervocalic consonant to the VCV part of the word measured lenition of the intervocalic /b/. .8 Second, the speed at which the intervocalic consonant was .7 released into the following vowel was measured as the .6 Stress Pattern difference between the maximum and the minimum .5 intensity of the consonants as function of time. When the Trochee formula results in a high number, it indicates that the .4 .3 Iamb consonant is released at faster speed and therefore, it is Ratio RMS realized as a stop. A lower number signifies a slower Spanish English release, which is more vowel-like. Speakers' Native Language

Figure 3: Degree of consonant lenition according to stress 3.2 INTERACTION OF INVENTORY contexts. For both phonetic factors Spanish consonants CONSTRAIINTS WITH STRESS displayed a higher overall degree of spirantization than did their English counterparts. This cross-linguistic difference The influence of stress in the degree of spirantization was reached significance only for the stress factor. constrained by consonant type. The interaction consonant*stress*language showed that in trochees, Spanish and English also differed in the effect of inventory Spanish /b/ was significantly more lenited than English /b/, constraints on consonant lenition. The interaction of while /g/ in Spanish and in English did not differ inventory constraints with stress showed that in trochees, significantly from each other. Spanish /b/ was more lenited than English /b/, while /g/ was equally lenited in both languages. 1.1 Finally, the influence of stress in consonant lenition was 1.0 captured by both measures of energy, i.e. RMS ratio and

.9 speed of consonant release, whereas the influence of vowel context was captured only by speed of consonant release .8 measures.

.7

.6 4. DISCUSSION Language .5 The phonetic factors of stress and vowel context had

.4 Spanish similar effects in the lenition of intervocalic /b/ and /g/ in Spanish and in English. Consonants are more spirantized .3 English RMS ratio /b/ /g/ when followed by a non-stressed vowel. This result parallels that of Cole et al. for Spanish /g/ [3] and DeJong in Consonant his study on English [6]. It is also consistent with research that has found that articulatory gestures reach a Figure 4: Degree of lenition of /b/ and /g/ in trochee words. greater magnitude in prosodically strong positions, while it is reduced in weak prosodic positions [7,8]. Therefore, 3.3 EFFECTS OF VOWEL CONTEXT these results reflect a well-established pattern that prosody Only the measures of speed of consonant release yielded influences the degree of segmental lenition. significant results for vowel context. A significant main As for vowel context, the results indicated that effect indicated that /a/ scored higher than /i/ and /u/ in both vowel-consonant coarticulation had an effect in /g/, not in languages. Moreover, the interaction consonant*vowel /b/; and that /g/ was most lenited in /i/-/u/ words and least in showed that these differences between /a/ and /i/-/u/ took /a/ vowel names. The lack of coarticulatory effects in /b/ place only in intervocalic /g/. Intervocalic /b/ did not reflect was expected given the independence of the articulators in any effect of vowel context in either language. producing each sound, i.e. lips for /b/ and tongue for the vowel [9,10]. 800 The results for /g/ agreed in part with those obtained by

600 Cole et al [3]. In both studies, /g/ obtained the most BA stop-like scores when flanked by vowel /a/, and the most lenited scores with /u/. However, for /i/ Cole [3] obtained 400 BI intermediate scores, while our results indicated a lenition BU degree equivalent to that of /u/. 200 GA These differences can be related to methodological issues between experiments. For example, Cole [3] clustered /i/ 0 GI with /e/ and /u/ with /o/ in their test materials, while this experiment included only /i/ and /u/. Moreover, Cole’s -200 GU Speed of Consonant Release results were based in RMS ratio measures, while in our Spanish English experiment only the speed of consonant release measures, Language not RMS ratio, yielded significant differences between vowel contexts. One possible explanation is that RMS ratio Figure 5: Degree of lenition of /b/ and /g/ according to measures captured energy changes sensitive to an average, vowel context. while speed of consonant release measures denoted changes of energy over time. Thus, RMS ratio measures In summary, the phonetic factors of stress and vowel were less sensitive to dynamic changes such as context had a similar effect in the degree of spirantization coarticulation effects than speed of release measures. of Spanish and English intervocalic consonants. Both /b/ and /g/ were more lenited in trochee words, and /g/ in /i/-/u/ In spite of the above differences, Cole’s [3] interpretation of the effect of vowel context as a consequence of the dynamic REFERENCES of tongue body movement (DTBM) is also valid for the results obtained in this paper. 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