Quality estimation of averaged auditory brainstem responses

In its clinical use, the auditory brainstem responses, ABR, are recovered from the background noise by averaging a number of post-stimulus time epochs, sweeps. Normally, the test protocol prescribes a fixed number of sweeps to be employed and recording of replications is frequently recommended, too. Since both the ABR and the background noise differ in magnitude among patients and test sessions, such a test protocol can never ensure a given minimum "quality" or signal-to-noise ratio, SNR, of the averaged ABR. In an attempt to solve this problem, a method is proposed to evaluate, in statistical terms, the "quality" or SNR of the averaged recording. This is done by calculating the ratio between the estimated magnitude of the ABR and that of the averaged background noise. The method can be employed "on-line" in an adaptive strategy to estimate the number of sweeps necessary to obtain a given minimum "quality" of the averaged ABR. It can be used in suprathreshold recordings as well as in automatic "threshold" detection and it is a practical tool to analyze and improve the cost-benefit of the ABR test.