| Popis: |
The objective methods of audiometry are based on the registration of noisy signals of small amplitude which are contaminated with interferences of diverse and variable sources. The reconstruction of the target signal is performed by selection and averaging of many signal epochs. Beyond these basic digital tools of signal processing, whose practical value is well-proven, other procedures which have never been established in commercial devices are potentially suitable to further improve the signal quality and the reliability of its detection. They are subject of this paper, as well as several new approaches, some of which have already been proven as useful in clinical practice while others are still awaiting their practical application. By implementation of these procedures, the precision and reliability of the diagnostic conclusions derived from otoacoustic emissions (OAE) and auditory evoked potentials (AEP) can be enhanced substantially.This review aims to exploit the potential of signal processing to the highest possible extent. Its main topics are a digital filter optimized for the detection of AEPs, the extension of averaging to the polarity of the signal, the extraction of parameters qualified as measures for quality and significance, and the time-differential analysis of correlation. Furthermore, the digital superposition of several independent recordings, the use of the amplitude distribution density and an algorithm developed to reduce the impact of residual noise on the response threshold are described for the first time. |
