Analysis of early auditory evoked potentials elicited by stimuli with directional information

A systematic evaluation of the influence of different averaging methods on the quality of recorded auditory brain stem responses is performed on a single sweep basis, i.e., on a post-hoc analysis of all unaveraged single epochs. The question of an optimal averaging method is addressed. Single sweeps of auditory brain stem responses were recorded to monaural and binaural click stimuli at levels of 20, 40 and 60 dBnHL. Recording sites were both mastoids and the forehead (Fz), the vertex (Cz) served as common reference electrode. Five averaging methods were applied to the same set of data to compare their capability to reduce the residual noise. In addition, the method of iterative averaging is introduced, which relies on an improved estimation of the noise of single epochs. A simulation allows a verification of the quality of the different averaging methods and estimators of signal, residual noise, and signal-to-noise-ratio given by those methods. It is shown that single-sweep-based estimation of residual noise and signal-to-noise ratio is superior to average-based estimation. Weighted averaging with one iteration step is the most favourable averaging method with respect to minimum residual noise and valid A modified version of this chapter was published in Z. Audiol. 40 (2), 62–85: Riedel et al. (2001): “Single-sweep-based methods to improve the quality of auditory brain stem responses. Part II: averaging methods”