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Biomedical subjects

O Ozdamar

Publications and source records attributed to O Ozdamar.

14 recordsLinked to original sources
PubMed1992

FFT-based digital tactile vocoder system for real-time use.

A microprocessor-based real-time digital vibrotactile vocoder system has been developed to train the deaf and for artificial hearing research. The system is composed of a microcomputer module with a digital signal processor, interface units and an attenuator/driver circuit. Live or digitised (stored or synthetic) speech is presented to the skin spectrally through a belt housing eight or 16 vibrators. Speech is processed in real time using a fast Fourier transform. The system is also capable of presenting any arbitrary spatiotemporal pattern on the skin for artificial hearing experiments. A preliminary experiment with a deaf subject indicates that the system is potentially an effective device for artificial hearing.

Biomedical Engineering↗
PubMed1991

Optimization of automated hearing test algorithms: simulations using an infant response model.

Computer simulation was used to evaluate several parameters of an automated hearing test algorithm in an attempt to optimize the algorithm for accuracy and efficiency. An infant response model was developed to guide the simulations. Test parameters of interest were starting intensity and stopping rule and their interaction with a measure that is thought to emulate infant reliability, probability of task orientation. Results indicated that stopping rule, within the ranges investigated, had little effect on accuracy but had major impact on efficiency. Starting intensity interacted with the hearing status of pseudosubjects in influencing accuracy. Accuracy was most influenced by probability of task orientation. The simulated test data are compared to data from infants and young children in the accompanying article so that the response model can be evaluated.

Algorithms↗
PubMed1990

Computer methods for on-line hearing testing with auditory brain stem responses.

On-line computer methods were developed and evaluated for automated hearing testing with auditory brain stem responses (ABR). The system contained (1) a response recognition unit which recognized the presence or absence of an ABR response and (2) a threshold tracking unit which adjusted stimulus intensity and determined the ABR threshold. Two methods, one nontemplate (variance ratio) and one template (cross-correlation), were evaluated for response recognition while three threshold tracking methods were explored: clinical, Békésy, and PEST (parameter estimation by sequential testing). Both response recognition and threshold tracking units were evaluated by computer simulations for on-line operation using a standard set of experimentally recorded ABRs. The results indicated that while all the response recognition methods were reasonably accurate, their on-line use resulted in significant differences in test efficiency due to differences in tracking methods.

Acoustics↗
PubMed1990

Classification of audiograms by sequential testing using a dynamic Bayesian procedure.

A new method for estimating audiograms using behavioral responses is presented. The method is based upon a modification of the Bayesian probability formula in which an outcome is predicted from a static set of events. In the new method, classification of audiograms by sequential testing (CAST), the probabilities of occurrence of audiogram patterns are dynamically updated according to the outcome of each test trial. Computer simulation using an infant response model suggests that the procedure is efficient, sensitive, and specific.

Algorithms↗
PubMed1989

The effects of vocoder filter configuration on tactual perception of speech.

Perception of synthetic speech continua through the sense of touch and audition was compared utilizing a 32-channel spectrally-oriented electrocutaneous vocoder display and standard auditory psychophysical procedures. Perception of a consonantal and a vocalic continuum was evaluated utilizing three vocoder filter configurations: logarithmic, linear, and average (geometric mean of logarithmic and linear). Results indicated a close correspondence between tactual and auditory discrimination and identification for the vowel (/a/-/e/) and the consonant (/sta/-/sa/) continuum regardless of the filter characteristics.

Deafness↗
PubMed1988

Computer system for quantitative evaluation of an electrotactile vocoder for artificial hearing.

A computer-controlled experimental electrotactile vocoder system is designed to evaluate quantitatively the transmission of speech information and to test various design options for tactual vocoders. The system is composed of a digital speech synthesizer, a digital vocoder, a computer-driven electrotactile display, and an adaptive controller for psychophysical experimentation. Samples of continua representing speech contrast types occurring in natural languages are synthesized by systematically manipulating selected subphonemic features. The synthesized speech stimuli are processed using a programmable vocoder and presented to the skin with an electrotactile display belt worn on the abdomen. Transmission of significant speech parameters is quantitatively evaluated using adaptive psychophysical techniques and labeling tests. The system is used to assess the potential of speech transmission through the skin and to evaluate different vocoder configurations and processing techniques for tactual vocoders to be used as artificial hearing devices by the deaf.

Adult↗
PubMed1988

Similarities between tactual and auditory speech perception.

Perception of synthetic speech continua through the sense of touch and audition was compared utilizing a 32-channel spectrally oriented electrocutaneous display and standard auditory psychophysical procedures. Results indicated a close correspondence between tactual and auditory discrimination and identification for a vowel (/a/-/e/) and a consonant (/sta/-/sa/) continuum. These results suggest that at least some aspects of speech perception are amodal.

Humans↗
PubMed1987

Hearing loss in an institutionalized mentally retarded population. Identification by auditory brainstem response.

We report the results of auditory brainstem response testing of 122 profoundly retarded institutionalized children, a segment of the retarded population heretofore generally regarded as untestable by behavioral audiometry. Major findings include: 32% of the study population showed, by auditory brainstem response, hearing loss exceeding 20 decibels of hearing level in one or both ears (12% showed conductive loss and 20% sensorineural loss); of the 15.6% with evidence of bilateral sensorineural loss, 7.37% had losses in the 30- to 50-dB range, and 8.19% had losses of 60 dB or greater; and evidence of abnormal brain-stem function was found in 11%. Results of otologic examinations and audiologic habilitative follow-up in selected children are also reported.

Adolescent↗
PubMed1987

Computer monitoring of auditory brainstem responses.

A relatively low cost, bedside, portable, microcomputer based system for long-term monitoring of human auditory evoked responses in critical care environments is described, and test data are presented. The system enables the user to acquire responses, detect significant peaks (usually peaks I, III, and V), store information and display trends (latency vs time graphs) automatically. Prior to processing, responses are digitally filtered so that no phase distortion is introduced. A peak detection algorithm takes into consideration both the different morphologies of the IV-V wave complex and the time-varying characteristics of the ABR waveform. Evaluations using normal subjects and intensive care unit patients show the clinical potential of automated long-term auditory brainstem monitoring.

Brain Stem↗
PubMed1986

Binaural interaction in the auditory middle latency response of the guinea pig.

Binaural interaction in the guinea pig middle latency response (MLR) was studied using two stimulus paradigms: binaural click stimuli and monaural click stimuli with contralateral white noise. During monaural click stimulation, the MLR is largest in amplitude over the contralateral temporal lobe. Binaural click stimulation reduces the amplitude of this response. Monaurally evoked click responses are also altered by the presentation of continuous white noise in the contralateral ear. The addition of white noise results in an increase in amplitude particularly of components A (12 msec) and B (17 msec). These alterations in response amplitude are specific to the MLR with no change occurring in the auditory brain-stem response (ABR). These findings appear to reflect interaction between the generators of middle latency response.

Acoustic Stimulation↗
PubMed1978

Behavioral, compound action potential, and single unit thresholds: relationship in normal and abnormal ears.

Comparisons were made for two species (chinchilla and mongolian gerbil) among mean behavioral audiogram, mean just detectable action potential (AP) responses to tone bursts, and single-fiber response thresholds at the characteristic frequency, averaged in one-octave bands. In normal animals and in a group of Kayamycin-treated chinchillas, these mean measures appear to have a well-ordered relationship. Unit and AP thresholds are within 10 dB from one another throughout the frequency range. Behavioral thresholds are usually 15--20 dB more sensitive, but the three curves are roughly parallel except at the highest frequencies, where the behavioral threshold begins to increase approximately one-half octave above the physiological ones. Individual examples for four gerbils and four chinchillas having hair cell losses due to Kanamycin intoxication reinforce the notion based on mean data that in most cases AP thresholds can serve to predict the behavioral threshold configuration.

Action Potentials↗