AUDITORY AND F-PATTERN VARIATIONS IN AUSTRALIAN OKAY: A FORENSIC INVESTIGATION
Jennifer Elliott
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Abstract An understanding of the acoustic properties, as well as the nature of within- and between-speaker variation, of words which occur with high frequency in natural discourse, is of great importance in forensic phonetic analyses. One word which occurs with relatively high frequency in natural discourse, including telephone conversations, which are often a source of data in forensic comparisons, is okay This paper presents the initial findings of a study of auditory and F-pattern variations in okay in a natural telephone conversation spoken by six male speakers of general Australian English. Seven pre-defined sampling points are measured within each token to determine the most efficient sampling points and formants for distinguishing between-speaker variation from within-speaker—variation in okay. F—ratios at these seven sampling points are calculated as a mean of ratios of between- to within-speaker variation. The greatest F-ratio is shown to be for F, at voice onset of the second vowel. Forensic implications are discussed.
COMPARING THE ACOUSTIC PROPERTIES OF NORMAL AND SHOUTED SPEECH: A STUDY IN FORENSIC PHONETICS.
Jennifer Elliott
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Abstract Forensic phoneticians are able to exercise little control over the data-they are required to examine and compare. When two speech samples, one from a criminal and one from a suspect, are provided for forensic analysis, it is quite possible that one sample may contain shouted speech, while the other will contain normally spoken speech. Analysing these dissimilar speech samples requires an understanding of how the acoustic properties of shouted speech differ from normal speech. This paper reports the findings of a pilot study which investigates the similarities and differences between the acoustic properties of natural speech in both normal and shouted modes. Results of the experiment indicate, that F0 and F1, may be significantly higher in shouted speech, but there as no evidence tor a significant difference in F-pattern for the other formants.
EFFECTIVE F2 AS A PARAMETER IN JAPANESE FORENSIC SPEAKER IDENTIFICATION
Yuko Kinoshita
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Abstract The possibility of using effective F2 as a parameter in forensic speaker identification is demonstrated. 11 male Japanese speakers were recorded, and the formants of their 5 Japanese accented short vowels were measured. The potential of effective F2 as a possible forensic speaker identification parameter was evaluated by Faratio. The results showed that effective F2 of /e/ produced considerably a higher F-ratio than individual F2 and F3 of the same vowel, although transforming into effective F2 did not improve the F-ratio of the other vowels.
STATISTICAL QUANTIFICATION OF DIFFERENTIAL VOWEL COMPARABILITY IN FORENSIC PHONETIC SAMPLES
Yuko Kinoshita John Maindonald
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Abstract In the phonetic comparison of forensic samples, vowels in different words often need to be compared. This paper discusses to what extent vowels embedded in different words are in fact comparable. The experiment was carried out on natural speech data to simulate forensically realistic conditions, and 11 male native Japanese speakers participated as informants. Multi-level analysis of variance was performed on the F2 of three vowels /a/, /i/, and /e/. The experiment shows that, although the phonological environment, namely the nasality of a preceding consonant, affects the F2 of these vowels, the magnitude of the effect can be discounted. What is shown to be important, however, is the identity of the vowel, and comparisons with /a/ in different phonological environments are strongly disfavoured.
COMPARATIVE PERFORMANCE OF CEPSTRUM AND FORMANT BASED ANALYSIS ON SIMILAR-SOUNDING SPEAKERS FOR FORENSIC SPEAKER IDENTIFICATION
Phil Rose and Frantz Clermont
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Abstract A pilot forensic-phonetic experiment is described which compares the performance of formant- and cepstrally-based analyses on forensically realistic speech: intonationally varying tokens of the word hello said by six demonstrably similar-sounding speakers in recording sessions separated by at least a year. The two approaches are compared with respect to F-ratios and overall discrimination performance utilising a novel band-selective cepstral analysis. It is shown that at the second diphthongal target in hello the cepstrum-based analysis outperforms the formant analysis by about 5%, compared to its 10% superiority for same-session data.