Edward Miskiel

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.

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.

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.

On-line system for automated auditory evoked response threshold determination

An online computer system has been developed to determine auditory-evoked-response thresholds for objective hearing testing of otherwise untestable patients. The system uses click-evoked auditory brainstem responses. Online threshold determination is accomplished by two modules: a response recognition unit which determines if a response is present and a threshold tracking unit which utilizes a modified PEST (parameter estimation by sequential testing) algorithm to determine the click intensity testing level. Thresholds obtained manually and automatically are compared in 161 tests from 62 ears. Results indicate that automatically obtained thresholds show a strong agreement with those obtained visually as determined by a panel of experts.<<ETX>>

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.

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.

Next Generation PERG Method: Expanding the Response Dynamic Range and Capturing Response Adaptation

Purpose To compare a new method for steady-state pattern electroretinogram (PERGx) with a validated method (PERGLA) in normal controls and in patients with optic neuropathy. Methods PERGx and PERGLA were recorded in a mixed population (n = 33, 66 eyes) of younger controls (C1; n = 10, age 38 ± 8.3 years), older controls (C2; n = 11, 57.9 ± 8.09 years), patients with early manifest glaucoma (G; n = 7, 65.7 ±11.6 years), and patients with nonarteritic ischemic optic neuropathy (N; n = 5, mean age 59.4 ± 8.6 years). The PERGx stimulus was a black-white horizontal grating generated on a 14 × 14 cm LED display (1.6 cycles/deg, 15.63 reversals/s, 98% contrast, 800 cd/m2 mean luminance, 25° field). PERGx signal and noise were averaged over 1024 epochs (∼2 minutes) and Fourier analyzed to retrieve amplitude and phase. Partial averages (16 successive samples of 64 epochs each) were also analyzed to quantify progressive changes over recording time (adaptation). Results PERGLA and PERGx amplitudes and latencies were correlated (Amplitude R2 = 0.59, Latency R2 = 0.39, both P < 0.0001) and were similarly altered in disease. Compared to PERGLA, however, PERGx had shorter (16 ms) latency, higher (1.39×) amplitude, lower (0.37×) noise, and higher (4.2×) signal-to-noise ratio. PERGx displayed marked amplitude adaptation in C1 and C2 groups and no significant adaptation in G and N groups. Conclusions The PERGx high signal-to-noise ratio may allow meaningful recording in advanced stages of optic nerve disorders. In addition, it quantifies response adaptation, which may be selectively altered in glaucoma and optic neuropathy. Translational Relevance A new PERG method with increased dynamic range allows recording of retinal ganglion cell function in advanced stages of optic nerve disorders. It also quantifies the response decline during the test, an autoregulatory adaptation to metabolic challenge that decreases with age and presence of disease.

Microsurgical laser Doppler probe for simultaneous intraoperative monitoring of cochlear blood flow and electrocochleography from the round window

The aim of this project is the development of a microsurgical laser Doppler (LD) probe that simultaneously monitors blood flow and Electrocochleography (ECochG) from the round window of the ear. The device will prevent neurosensory hearing loss during acoustic neuroma surgery by preventing damage to the internal auditory nerve and to the cochlear blood flow supply. A commercially available 0.5 mm diameter Laser-Doppler velocimetry probe (LaserFlo, Vasamedics) was modified to integrate an ECochG electrode. A tube for suction and irrigation was incorporated into a sheath of the probe shaft, to facilitate cleaning of the round window (RW) and allow drug delivery to the round window membrane. The prototype microprobe was calibrated on a single vessel model and tested in vivo in a rabbit model. Preliminary results indicate that the microprobe was able to measure changes in cochlear blood flow (CBF) and ECochG potentials from the round window of rabbits in vivo. The microprobe is suitable for monitoring cochlear blood flow and auditory cochlear potentials during human surgery.

Effects of filter configuration on categorical perception of tactually presented speech

The effect of filter configuration on the relationship between auditory and tactual perception of speech was investigated via a 32‐channel computer controlled electrocutaneous display and normal audition. Two 11‐step synthetic speech continua, /a/ to /ə/ and /sta/ to /sa/, served as stimuli for study of three filter configurations: logarithmic, linear, and average (arithmetic mean of log and linear). Four well‐practiced subjects performed two tasks with each stimulus continuum and each filter configuration: (1) a standard identification procedure where all 11 steps are categorized as either endpoint 1 or 11, and (2) a pairwise discrimination task (where equal interval stimuli were discriminated across the continuum). The same tasks were presented in the auditory modality for comparison purposes. Results indicate (1) a close correspondence between tactual and auditory perception, (2) categorical perception of the consonontal continuum and more continuous perception of the vowel continuum in both modalities...

Comparison of tactual and auditory discrimination of speech

The relationship between tactual and auditory perception of speech was investigated by presenting two speech continua to subjects via a 32‐channel computer controlled electrocutaneous display and via normal audition. The stimuli were synthetic /a/ to /ə/ and /sta/ to /sa/ with 9 equally spaced intermediate stimuli between each endpoint yielding two 11‐step continua. Five well‐practiced adults performed three tasks: (1) an adaptive discrimination task using each of the endpoints as target stimuli; (2) a standard identification procedure (all 11 steps categorized as either endpoint 1 or 11); and (3) a same‐different task (equal interval stimuli were discriminated across the continuum). For tactual discrimination, channel information was presented in three spectral configurations conforming to (1) logarithmic, (2) linear, and (3) average (arithmetic mean of log and linear) filtering. Results indicate (a) a close correspondence between auditory and tactual perception, (b) subphonemic discrimination in both mo...