Hearing Impairment Simulation for the Performance Evaluation of Hearing Aid / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: With the advent of high speed digital signal processing chips, many digital techniques have been introduced to hearing aids. Generally, subject-based clinical tests are needed to verify the performance of hearing aids, which required both time and cost. A hearing impairment simulation (HIS) system is developed in real-time system which is aimed to simulate the sensorineural hearing impairment. In this paper, we present an indirect method to evaluate and predict the performance of hearing aid systems without the help of actual subjects. MATERIALS AND METHODS: The system is developed based on the model constructed from auditory test results and nonlinear behaviors of sensorineural hearing impaired persons. To verify the proposed system, signals processed were presented to normal listeners and their auditory data modified by the system were measured and compared with those of the impaired models. RESULTS: The auditory data of models were closely simulated to normal listeners by HIS system in all frequencies especially to those with hearing loss of more than 60 dB. CONCLUSION: HIS System can be used clinically in developing new digital hearing aid algorithm.

Development of a computerized EEG imaging system with a personal computer

The authors developed a computerized electroencephalography imaging system with an IBM PC AT. The EEG signals amplified with a 16 channel EEG machine were digitized at 51.2 Hz (512 samples per epoch). The shifted DC potential and 60Hz artificats were removed by a high pass filter and 60Hz notch filter. A window function consisting of a 10% cosine taper was obtained by weighting the points at either end of the epoch by a cosine bell. A fast Fourier transform was applied to every epoch and the power spectrum estimates were computed in 0.39 Hz steps. The activity estimates for the delta, theta, alpha and beta bands were computed by summimg adjacent values. The outline of the top-down maps was formed from a series of sagittal cuts, then 32 electrodes were placed on the map. A file was created which contained a table of weighting parameters for calculating the interpolated values for every point within the outline. Each weight was in inverse linear proportion to the distance of the pixel to the nearest four electrodes. The map was finally generated with computation of the spectral EEG in each pixel according to the weighting parameter. The functioning of this system was tested with a functional generator and a human subject.

Cementless Press-Fit and Fibrous or Bony Ingrowth "Asian Total Hip Prosthesis" Design Using Computed Axial Tomography and Computer Aided Design and Computer Aided

The purpose of this study was to design intramedullary femoral stems that will optimally distribute the stresses to the bone. It was postulated that an ideal distribution of stresses would occur if the femoral stem had the same shape as the canal. However, because of the curved nature of the canal it was not possible to insert a canal replica. To make insertion possible, certain areas on the stem must be removed. Cross-section of the femoral canal at 5 and 10mm intervals, were non-destructively obtained by computer assisted tomography and each outline was stored on computer disk. Close-fit stem shapes were generated by computer aided design. These close-fit hip stem designs significantly improved total and priority region stem-canal contact. Further investigation employing both theoretical analysis and laboratory experimentation will examine the strength of these stems and theirs stress distribution to the femur.