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Original scientific paper
Gordana Varošanec-Škarić, This email address is being protected from spambots. You need JavaScript enabled to view it., Filozofski fakultet u Zagrebu
Gabrijela Kišiček, This email address is being protected from spambots. You need JavaScript enabled to view it., Filozofski fakultet u Zagrebu

 

Abstract

Upon the request of the County Court of Zagreb, on the basis of the recordings obtained by the police eavesdropping of the GSM device, the identification of a male voice was to be performed. The male voice from the recording No. 1 – duration of 2.16 min (CD 1) had to be compared with the male voice from the recording No. 2 – duration 7.39 min. The whole material was phonetically transcribed for the purpose of examining regional pronunciation, dialect and idiolect. For the purpose of sound analysis, dubbing was performed as well. Linguistic analysis has shown the difference in the use of idiosyncratic words, as well as the difference on the phonological level. For instance, recognized speaker used word jaran 69 times (which is 170 times more that in the usage of Croatian language). In the sample of two recordings with the recognized speaker, idiosyncratic meaningful words show significantly more frequent absolute and relative appearance when compared with the appearance in Croatian language. Those words didn’t appear in the sample of the second speaker, but the recordings had some other words that coincided. Although the phonetic and linguistic analyses differ, they are tightly connected. According to the forensic phonetics protocol (SPID, Hollien 2002, Varošanec–Škarić, 2008), auditory perception analysis of speech show high possibility of male person identification, i.e. experts’ recognition was 96% in range from G. Varošanec–Škarić, G. Kišiček, Fonetsko forenzičko prepoznavanje ... – SL 73, 89–108 (2012) 108 94% to 98%. Recognized speaker belongs to the group of stakavian ikavian Bosnian speeches: syntactically and morphologically that is eastern Bosnian variant (specific use of present tense, instead of negation plus infinitive he uses the typical form, he is shortening infinitives, omitting initial [x. Phonetically, on the suprasegmental level of accent realization, the recognized speaker uses marked accents of the eastern stakavian variant (longer long–rising accent and after–stress length), he is shifting falling accents from the meaningful words to the proclitic, and on the segmental level his pronunciation of vowels is typical for stokavian dialect. Vowels are realized more forward and closed than those of cardinal vowels of Croatian Received Pronunciation, reduction and after–stress omitting of vowels appear. Phonetic description of voice shows slightly higher voice, narrow jaw aperture, dentalization, and modal phonation type. Furthermore, formant analysis of all vowels was made for both speakers (F2, F3), while vowel /a/ provided the analysis of F1 as well, because its average values are around 800 Hz and is not affected by the distortion of transmission. Formant analysis based on the stresses vowels has shown the difference (z–test) when compared with standard Croatian Pronunciation (for lower F1 /a/: p = 0,001, F2 higher for /a/, /e/, /o/, /u/) and in comparison with the other speaker F2 was higher for vowel /i/ (p = 0,08), F3 lower for vowel /o/ (p < 0,001). Long average spectra of speech that give information about voice timbre are different for those two speakers. Typical distortions in lower and higher parts of the spectrum during the transmission via GSM device were taken into consideration. According to Harmegnies (1995) similarity index (R) was calculated for two spectra from different recordings of the same identified male speaker was 0.91 and dissimilarity index (SDDD) was 0.96. In pair with unknown speaker R was in range from 0.75 to 0.88 and SDDD in range from 3.32 to 4.50. According to total results it can be concluded that male speaker was identified with a high rate of identification probability.

 

Key words

speaker identification, formant frequencies, speaker identification protocol, forensic phonetics, forensic linguistics

 

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