engleski

Comparison of F0 measures for male speakers of Croatian and Serbian

Fundamental frequency is, among other voice qualities, important in speaker identification (Traunmüller and Eriksson, 1995), especially because the F0 values are preserved in different recording conditions. An average F0 value for 104 male speakers of Croatian language is stated based on continuous neutral speech, with a duration of around 70 s and it is 117.36 Hz (setting between 75 and 176 Hz ; S.D. 18.78 Hz) (Varošanec-Škarić, 1998) ; for male speakers of Serbian language Jovičić (1999) reports average value of 121 Hz and S.D. F0 ca. 16 Hz, measured for five standard vowels of Serbian language. The author did not state the size of the sample of subjects and how many times the vowels have been repeated. Our goal was not to question previously measured values, but to measure F0 values which are important in acoustic and forensic phonetics. The aim of this paper was to compare fundamental frequency measures expressed in Hz and in semitones which can be used for more robust, future speaker comparison. Second, pragmatic aim of this paper was to collect samples of voices in order to create Croatian database which could be used in future for comparison based on sex, age, education, voice health between speakers of very similar languages, eg. Croatian, Serbian, Bosnian, Montenegrin and for comparison between Croatian speakers with received and dialectal pronunciation. It was expected that the younger groups of Croatian and Serbian speakers will not differ significantly for average value mean F0 and that the groups will differ more in acoustic variables which will be more affected by intonation, in median F0, baseline and in maximums. Method The same number of younger speakers, which are estimated to speak received Croatian and Serbian, has been chosen for both groups: Croatian (n=37) and Serbian (n=37), average age 21.6 (median 21) and 22 (median 22), respectively. Speakers were recorded under the same conditions during 2015 in the capitals of the two countries, Zagreb and Belgrade. Participants were recorded reading passage (ca. 2 min) and spontaneous spoken utterance (ca. 2 min) which were used for fundamental frequency measures in Hz and semitones. F0 mean, median, average baseline value Fb (based on median), average minimal and maximal F0 values, alternative baseline (Alt_Fb), standard deviation (S. D.) of F0 in both Hz and semitones were calculated. For the calculation special programs in Praat (Boersma and Weenink, 2015 ; Ver. 6.0.05) were used. The calculation was done on a limited setting between 65 and 300 Hz to get all the possible frequencies for the F0 range and to avoid octave jumps. Lindh (2006) used the setting between 75 and 350 Hz for the F0 tracker. Considering that the sample was comprised of only male speakers of received Croatian and Serbian without noticeable dialectal pronunciation, it has been shown that it is enough to limit the pitch ceiling to 300 Hz. The values above 300 Hz have been checked in preliminary testing and it has been show that they are discontinuous octave jumps, harmonics and stridents. Anova: Two-factor With Replication was used to test the differences between groups and to test the difference between reading passage and spontaneous spoken utterance. Results and discussion Respectively the greatest difference between groups was in median F0 in semitones (p=0.0005 ; Figure 1) and in Hz (Croatian 117.25 Hz, Serbian 124.09 Hz ; p=0.0007). It has been shown that 80 younger Croatian speakers have significantly lower F0 mean in both measurements than Serbian (Croatian 117.11 Hz, Serbian 126.64 Hz ; p=0.001), significantly lower Fb (Croatian 90.86 Hz, Serbian 97.30 Hz ; in Hz: p=0.001 ; in semitones: 0.002) and lower Alt_Fb. The overall results for both groups of speakers show less significant differences between reading passage and spontaneous spoken utterance for measures in semitones and in Hz for Fb (p=0.017 ; 0.015), respectively, median F0 (p=0.014 ; 0.018), for F0 minimums (in Hz, p=0.016 ; 0.022), for F0 mean (p=0.02 ; 0.024), for F0 maximums (Croatian 198 Hz, Serbian 201 Hz ; p=0.04) and in semitones for Alt_Fb (p=0.04). The values of F0 mean from this paper correspond with the value reported in Varošanec-Škarić (1998) for Croatian speakers, and for Serbian speakers it is somewhat higher than the F0 value reported in Jovičić (1999). It can be concluded from the collected data that intonation patterns are more different between groups of Croatian and Serbian speakers which is important for further research in the two similar languages. Overall, it can be concluded that clearer differences were found in the semitone measures, but both type of measurements, Hz and semitones, are useful for comparing speakers with different mother tongues. Regardless of the prevalence of the younger age group in criminal activities, it is not prevalent in real cases which phoneticians receive for identification in Croatia. Younger males are present in a lesser percentage than the middle age group between 40 and 50 years of age, which depends on type of criminal activities which are sent to phoneticians. Therefore, a comparison of younger and older speakers, whose voices will be gathered, is planned, at least for the Croatian population.

f0; male speakers; Croatian; Serbian; median

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