A rabic Speech Rhythm Corpus: Read and Spontaneous Speaking Styles (2020)

Abstract: Databases for studying speech rhythm and tempo exist for numerous languages. The present corpus was built to allow comparisons between Arabic speech rhythm and other languages. 10 Egyptian speakers (gender-balanced) produced speech in two different speaking styles (read and spontaneous). The design of the reading task replicates the methodology used in the creation of BonnTempo corpus (BTC). During the spontaneous task, speakers talked freely for more than one minute about their daily life and/or their studies, then they described the directions to come to the university from a famous near location using a map as a visual stimulus. For corpus annotation, the database has been manually and automatically time-labeled, which makes it feasible to perform a quantitative analysis of the rhythm of Arabic in both Modern Standard Arabic (MSA) and Egyptian dialect variety. The database serves as a phonetic resource, which allows researchers to examine various aspects of Arabic supra-segmental features and it can be used for forensic phonetic research, for comparison of different speakers, analyzing variability in different speaking styles, and automatic speech and speaker recognition.

## introduction the successful collection of data is a key stage to obtain reliable and valid results in phonetic research. in this paper, we report on work-in-progress about the construction of a speech corpus for arabic in egyptian dialect. the primary intention behind designing such a corpus is to provide a homogeneous database of arabic speech recordings, which investigates broadly/narrowly acoustic parameters of arabic speech rhythm for forensic voice comparison (fvc) research and casework application. in a typical fvc casework, two samples of voices, a known and an unknown (disputed) sample, are compared to estimate the probability that the same speaker has produced the speech samples (same-speaker hypothesis) versus the probability that the speech samples have come from two different speakers (different-speaker hypothesis) @xcite . to objectively estimate this probability, having access to speech corpus containing samples from arabic native speakers that contributes to the knowledge about between-speaker variability and within-speaker variability @xcite . the motivation for exploring speaker-specific acoustic properties of speech of arab speakers stems precisely from the lack of population statistics for the arabic language in fvc. as yet, to the best of our knowledge, there is no forensically relevant arabic speech corpus available being capable of utilizing in fvc research. the current corpus fitted for fvc research aims to fill this gap and it can be considered as the first database of its kind in arabic which consists of highquality audio recordings from a regionally and socially stratified population involving different speaking styles. the corpus follows principles of the protocol for the collection of databases of recordings for forensic-voicecomparison research and practice, which was developed by @xcite . based on the protocol requirements, a dataset can be suitable for fvc research which fulfills three criteria: 1) non-contemporaneity of recording sessions for each speaker, 2) using different speaking styles for the recordings of each speaker, and 3) usability for research and casework involving recording and transmission-channel mismatch. one of the promising and newly developed lines of investigation for fvc extracts speaker-specific information from the temporal organization of speech. recent evidence from numerous different languages has shown that speech rhythm characteristics based on consonantal and vocalic durational variability as well as syllabic intensity have potential in capturing betweenspeaker variability @xcite @xcite . the present study will, therefore, incorporate speech rhythm measures into the dataset by following the collection procedures of bonntempo corpus @xcite , which is one of the databases currently available for the study of speech rhythm measures in connection with speech rate. the current corpus will thus be an extension to bonntempo corpus, which subsequently allows us to investigate temporal characteristics of speech in msa from both an acoustic and speaker-specific point of view in future projects. ## corpus analysis and annotation speech tokens were analyzed using praat (version 5.3.78) @xcite . firstly, segments on-and offsets were labeled manually using praat's annotation function. the utterances were phonemically transcribed with ipa symbols. we used the waveform, spectrogram and auditory discrimination cues in determining phoneme boundaries. consonantal and vocalic intervals are, next to the syllables, the most central and most often used units of speech for rhythmic measurements in speech @xcite . for this reason, we annotated our data based on the aforementioned units. cv intervals were created automatically using an automatic script cv creator tier. a c-interval consists of one or more consonants preceded and followed by a vowel or by a pause whereas a v-interval consists of one or more vowels (or vocalic segments like diphthongs, triphthongs, etc.) preceded and followed by a consonant or by a pause @xcite . cv intervals comprise three tiers, (a) a tier containing consonantal and vocalic segments, (b) a tier containing consonantal and vocalic intervals with each interval containing the number of underlying consonantal and vocalic segments respectively and (c) a tier containing consonantal and vocalic intervals. the syllable tier was also labeled manually by trained phoneticians by following arabic phonotactic rules for syllabification (see figure 3 ) all five tempo versions (s2, s1, no, f1, f2) of each speaker have been saved in wav format in one file each (see figure 2 ). the file names contain information about the native language of the speaker in capital letters (e.g. 'ar' for arabic), speaker number, and the speaking tempo (e.g. 'no' for normal). language, speaker's number, and tempo information are separated by an underscore (e.g.: ar_01_no.@xmath0, number 1, intending to read in normal tempo). the entire recorded corpus was transcribed orthographically because of many reasons; first, it provides further researchers with a simple symbolic representation of the recorded data. with this representation, it is easy to navigate through the corpus. secondly, the orthographic transcription formed the basis for all other transcriptions and annotations. thirdly with regard to rhythmic measurers, the extraction of interval duration from speech relies mostly on manual inspection of waveforms and spectrograms and is therefore subject to the vagaries of individual researchers, who may use different criteria or apply common criteria idiosyncratically. the use of automatic methods of extraction is a clear first step for maintaining consistency. the annotation work for each speaker has been saved in praat label files of the type 'textgrid'. for each wav file there exists one textgrid file with the same file name but respective extension (e.g. ar_01_no_r_01.textgrid). ## conclusion in this paper, we presented the development of a homogeneous database for arabic in egyptian dialect, specifically designed for fvc tasks. we collected our corpus based on a) the protocol for the collection of databases of recordings for forensic-voice-comparison research and practice and, b) bonntempo corpus. we plan to conduct research on between-and within-speaker variability of supra-segmental acoustic parameters in our database. we also aim to study the degree to which acoustic cues vary across different speaking styles and what affects this variability has on speaker identification. as well as dealing with forensic issues, which is our primary goal in this project, the described database paves the way for addressing a number of theoretical and practical issues in acoustic phonetics of the arabic language. this database is supposed to be developed further and we aim to increase the number of speakers and speaking styles in the future. as there are many varieties of colloquial arabic, some are mutually intelligible, while others are not and the larger the physical distance between the dialects, the more a difference appears among them @xcite . for the future extension of the corpus, other arabic dialects like morocco and jordan arabic are planned to be recorded with the same procedures for arabic dialects comparison.