Auditory brain stem response for objective measures of hearing.

The auditory brain stem response (ABR) is felt to be an objective technique for predicting hearing thresholds because a voluntary response is not required from the subject. However, determination of ABR threshold can be a subjective process. This article discusses a technique, termed Fsp, which adds objectivity to ABR threshold detection by creating a ratio of signal plus averaged background noise over an estimate of the averaged background noise for any given averaged ABR. Fsp values have an F distribution. Consequently, the confidence of true detection for a given ABR can be determined by comparing its calculated Fsp value to statistical tables. Using a technique such as Fsp not only adds objectivity to ABR threshold detection, but also optimizes test time by allowing the averaging process to stop as soon as the background noise has been reduced and the true neural potential can be judged to be present. The estimate of the background noise can be used as a weighting factor to reduce the influence of noisy segments during the averaging process as well. Using this technique, we have found ABR threshold to be within 5 or 6 dB of psychophysical threshold for like (click) stimuli and, in our pediatric clinic, ABR click thresholds are within 10 dB of puretone average for children with losses ranging from mild to profound.