Speech perception test for Arabic-speaking children.

The high incidence of hearing impairment in the Arabic-speaking population in Israel, as well as the use of advanced aural rehabilitation devices, motivated the development of Arabic speech assessment tests for this population. The purpose of this paper is twofold. The first goal is to describe features that are unique to the Arabic language and that need to be considered when developing such speech tests. These include Arabic diglossia (i.e., the sharp dichotomy between Literary and Colloquial Arabic), emphatization, and a simple vowel system. The second goal is to describe a new analytic speech test that assesses the perception of significant phonological contrasts in the Colloquial Arabic variety used in Israel. The perception of voicing, place, and manner of articulation, in both initial and final word positions, was tested at four sensation levels in 10 normally-hearing subjects using a binary forced-choice paradigm. Results show a relationship between percent correct and presentation level that is in keeping with articulation curves obtained with Saudi Arabic and English monosyllabic words. Furthermore, different contrasts yielded different articulation curves: emphatization was the easiest to perceive whereas place of articulation was the most difficult. The results can be explained by the specific acoustical features of Arabic.

A targeting-and-extracting technique to enhance hearing in the presence of competing speech.

A targeting-and-extracting procedure of speech enhancement for hearing aids in the presence of background noise, especially competing speech, is proposed. The procedure is composed of two steps: targeting by a fixed (or deterministic) beamforming array, followed by a post-targeting extracting step. Emphasis is placed on the extracting step, which performs noise cancellation based on the acoustic difference between the desired speech and interfering speech. Either comb filtering or attenuation is applied to the signal in accordance with the current voiced/unvoiced/silence state of the desired signal. The comb filter design is based on the fundamental pitch frequency of the desired speech. Algorithms for deciding the voiced/unvoiced/silence state and determining the fundamental frequency are developed. The performance of the system is evaluated through computer simulation. The simulation results indicate significant noise cancellation and intelligibility improvement.

[Effect of polypectomy on voice quality].

Voice quality and improvement after vocal cord polypectomy was assessed in 15 patients. The polyps were found by indirect observation; assessment of vocal quality was by recording isolated vowels, words and sentences said in Hebrew before operation and 1 and 3 months later. The recordings were analyzed using a computer program written at the Medical Electronics Laboratory of The Technion. Analysis of the 5 Hebrew vowels (a,e,i,o,u) yielded numerical and graphical data of formats specific for each utterance and speaker. These data were compared with control data taken from the literature for healthy Hebrew speakers. Statistical analysis (by paired t-test for matched samples) revealed a tendency to a decrease in difference between postoperative results and control data. Comparison of preoperative recordings with control data suggest that this method of voice condition assessment is worth considering for systematic application in clinics and hospitals. Among its advantages is that it permits long-term objective assessment of changes in voice quality. It thus supplies data for follow-up studies of patients and others who suffer from voice problems, especially those whose voice is their professional tool.

Pitch perception in patients with a multi-channel cochlear implant using various pulses width.

Cochlear implants have been designed to partially restore hearing to those people who are totally deaf. Multi-channel cochlear implants offer the opportunity to evoke acoustic perceptions like loudness and pitch, elicited by a controllable pattern of electric stimulation by means of electrodes placed in different places along the cochlear length. In this study, two psychophysical experiments were conducted with 4 patients, 1 prelingually and 3 postlingually-deafened, implanted with the multi-channel cochlear prosthesis Nucleus 22. Experiments were carried out to study the effect of varying the width of the electric biphasic pulsatile stimuli on the discriminative abilities of the pitch perception. The tests involved place pitch ranking and pulse rate discrimination. Place pitch ranking was studied by determining the just noticeable difference in pitch pairs (jnd-pp), defined as the pair of nearest electrodes which elicit different pitch perception. Pulse rate discrimination was studied by determining the just noticeable difference in pulse rate (jnd-pr) defined as the minimal difference in stimulus repetition rate over a given electrode, which elicits different pitch perceptions. Both experiments were conducted using pulses of 400, 200, 100 and 50 microseconds/phase. The results indicated that in spite of the differences in pathologies and personal histories, both jnd-pp and jnd-pr decrease by diminishing the pulse width. Speech perceptual data, measured for various pulse widths, validates the usefulness of decreased pulse width which yields favorable results in the psychophysical tests.