Kanae Amino

Speaker-dependent characteristics of the nasals

Investigation on human speaker identification enables us to know the indexical cues to speakers, and it may consequently lead to the effective acoustical parameters that can be used for forensic speaker recognition. It is known that speaker individuality interacts with the phonological or linguistic information contained in speech signals. As proof, the accuracy of perceptual speaker identification (PSI) performances depends on what types of sounds are presented to the listeners. In a series of our previous experiments, we have been investigating the effective sounds for PSI, and the stimuli containing a nasal were found to be the ones. In this present study, we conducted another PSI experiment in order to examine the reproducibility of the nasal effectiveness, and to see the effects of the following vowels. Coronal nasals were shown to be effective despite the different speaker set or the following vowels, and the stimuli containing a nasal were significantly better than those without it. In the second part of this paper, we introduce the results of the acoustical analysis of the stimuli. The contours of the energy transitions showed variations in shape among speakers for all three types of the analysis targets; nasals, stops, and fricatives, although the inter-speaker difference in the energy slopes for the consonant articulation was significant especially in nasal sounds. We also examined the effects of the sampling frequencies and the speech codecs, and found that the speaker-dependent shapes of these energy contours were maintained as long as the speech materials were uncompressed. The contours of the nasals appeared to be stable within a speaker, compared to other types of sounds.

Differential effects of the phonemes on identification of previously unknown speakers

In perceptual speaker identification, it is known that the identification accuracy depends on the contents of the stimuli presented to the listeners. In our previous experiments, we found that the stimuli containing a nasal sound are effective for human speaker identification, and that coronal sounds are more effective than labial ones. This tendency was observed in the identifications of both familiar and previously unknown speakers. In this present study, we investigated the effects of the speech contents again, by focusing on the vowels in CV monosyllabic stimuli. Through the experiment we obtained several findings: 1) stimuli containing a nasal gained significantly higher accuracy compared to stimuli with only oral sounds; 2) coronal sounds were more effective than labial sounds; 3) palatalisation caused an improvement in performance; and 4) back vowels were more effective than front vowels significantly. These results can be explained by speaker‐specific morphologies of the nasal cavity and the paran...

Effects of the Phonological Contents on Perceptual Speaker Identification

It is known that the accuracy of perceptual speaker identification is dependent on the stimulus contents presented to the subjects. Two experiments were conducted in order to find out the effective sounds and to investigate the effects of the syllable structures on familiar speaker identification. The results showed that the nasal sounds were effective for identifying the speakers both in onset and coda positions, and coronal sounds were more effective than labial counterparts. The onset consonants were found to be important, and the identification accuracy was degraded in onsetless structures.

Phoneme dependency of accuracy rates in familiar and unknown speaker identification

For perceptual speaker identification, the identification accuracy depends on the speech contents presented to subjects. Our previous studies have shown that stimuli containing nasals are effective for identifying familiar speakers [Amino et al., Acoust. Sci. Tech. 27(4) (2006)]. We have also presented the possibility that the interspeaker spectral distances reflect perceptual speaker similarities. In the present study, we conducted an experiment in which four unknown speakers were identified by 15 subjects. The stimuli were identical to those used in the previous study, in which ten speakers were identified by familiar listeners, although the speakers were fewer this time. Nine consonants in the CV structure were used as stimuli. The consonants were /d/, /t/, /z/, /s/, /r/, /j/, /m/, /n/, and /nj/; the vowel was restricted to /a/ for all CV syllables to simplify the experiment. The results showed that the nasals /n/ and /nj/ obtained higher scores. Tendencies in the differences among consonants were on the same order as those of the previous experiment, but the average scores were lower than those for familiar listeners. [Work supported by Grant‐in‐Aid for JSPS Fellows 17‐6901.]