Frequency Matters: Pitch Accents and Information Status

Proceedings of the 12th Conference of the European Chapter of the ACL, pages 728–736, Athens, Greece, 30 March – 3 April 2009. c⃝2009 Association for Computational Linguistics Frequency Matters: Pitch Accents and Information Status Katrin Schweitzer, Michael Walsh, Bernd M¨obius, Arndt Riester, Antje Schweitzer, Hinrich Sch¨utze University of Stuttgart Stuttgart, Germany <firstname>.<surname>@ims.uni-stuttgart.de Abstract This paper presents the results of a series of experiments which examine the impact of two information status categories (given and new) and frequency of occurrence on pitch accent realisations. More specifi- cally the experiments explore within-type similarity of pitch accent productions and the effect information status and frequency of occurrence have on these productions. The results indicate a significant influence of both pitch accent type and information status category on the degree of within- type variability, in line with exemplar- theoretic expectations. 1 Introduction It seems both intuitive and likely that prosody should have a significant role to play in marking information status in speech. While there are well established expectations concerning typical asso- ciations between categories of information status and categories of pitch accent, e.g. rising L∗H accents are often a marker for givenness, there is nevertheless some variability here (Baumann, 2006). Furthermore, little research has focused on how pitch accent tokens of the same type are re- alised nor have the effects of information status and frequency of occurrence been considered. From the perspective of speech technology, the tasks of automatically inferring and assigning in- formation status clearly have significant impor- tance for speech synthesis and speech understand- ing systems. The research presented in this paper examines a number of questions concerning the relationship between two information status categories (new and given), and how tokens of associated pitch ac- cent types are realised. Furthermore the effect of frequency of occurrence is also examined from an exemplar-theoretic perspective. The questions directly addressed in this paper are as follows: 1. How are different tokens of a pitch accent type realised? Does frequency of occurrence of the pitch ac- cent type play a role? 2. What effect does information status have on realisations of a pitch accent type? Does frequency of occurrence of the informa- tion status category play a role? 3. Does frequency of occurrence in pitch ac- cents and in information status play a role, i.e. is there a combined effect? In examining the realisation of pitch accent to- kens, their degree of similarity is the characteristic under investigation. Similarity is calculated by de- termining the cosine of the angle between pairs of pitch accent vector representations (see section 6). The results in this study are examined from an exemplar-theoretic perspective (see section 3). The expectations within that framework are based upon two different aspects. Firstly, it is expected that, since all exemplars are stored, exemplars of a type that occur often, offer the speaker a wider selection of exemplars to choose from during pro- duction (Schweitzer and M¨obius, 2004), i.e. the realisations are expected to be more variable than those of a rare type. …

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