Pairs Of Talkers Research Articles

Frequency perturbation and duration characteristics of pathological and normal speakers

The purpose of this study was to determine if measures of speaking fundamental frequency and its perturbation, as well as selected durational aspects of speech may be used to discriminate normal from abnormal phonation, specifically, in five pairs of talkers matched for age. A spoken sentence and sustained /a/ provided the sample for the acoustic analyses. Fifty glottal waveforms from each subject were measured to determine the mean perturbation of the fundamental frequency for the sustained vowel. The best predictor variables for these subjects from the seven variables analyzed were found to be the vocalic duration of the sentence segment and the mean perturbation for sustained vowels.

Perceptual (aural) and spectrographic investigation of speaker homogeneity

In order to investigate the perceptual and spectrographic homogeneity of speakers, 28 (14 pairs) talkers recorded an extended prose passage on two occasions, one week apart. Twelve talkers were chosen as six pairs on the basis of their having been confused with each other due to the similarity of their voices. A tape was prepared for the presentation of two randomized 2-sec speech segments for each pair of talkers. Listeners made aural/perceptual judgments of same or different for the following conditions: (1) same/contemporary (i.e., one talker recorded at the same time); (2) same/noncontemporary (i.e., one talker recorded one week apart); (3) different (i.e., paired talkers). Preliminary analysis of the data indicate the following: (1) 96% correct identifications were obtained for the same talker paired with a contemporary speech segment; (2) 44% correct identifications were obtained when comparing the same talker with a noncontemporary speech sample; (3) 87% correct identifications were obtained when comparing different talkers of a pair; (4) confusions between contemporary and noncontemporary samples of talker pairs occurred at a 38% level. High identification scores were expected for categories 1 and 3. It is evident that correct identification of a talker drops sharply when the comparison speech sample is noncontemporary. Further research duplicated the above procedure utilizing the same speech samples filtered to match a telephone passband; results were similar to the above. Spectrographic matching will be done for both procedures and results from each will be correlated.

Theory for Some Asynchronous Time-Division Switches

A two-wire active asynchronous time-division switch has recently been proposed by J. O. Dimmick, T. G. Lewis, and J. F. O'Neill. The interrupted energy transfer from one filter to another is accomplished asynchronously in order that more efficient use may be made of processing time of talker pairs on the switching bus. After first formulating, in a concise mathematical fashion, the effect of passing a signal through such a randomly time-varying circuit, we focus attention on optimizing an important filter response function. Typically, two percent rms jitter in the transfer times yields αn output S/N of 30 dB independent of signal spectrum. The timing stabilization required to obtain small jitter is also discussed and an exact solution for exponential processing time is obtained. This latter result may be put to good use in studying the efficiency of the switch. Conservatively, asynchronous operation should increase traffic capacity threefold. Finally, a speech wave which passes through a sample-and-hold circuit with random sampling times is considered upon being reconstructed with a fixed filter. This is a model for a four-wire active asynchronous switch, and results are compared with the two-wire situation.