ABR

[GEM]

When calculating the average noise to determine if the response reaches the 3:1 criteria should the noise be averaged across the waveform or the entire recording window?

[Guy]

The final wording of the NHSP ABR guidance will be "the noise level can be estimated from the average difference between the traces for the whole recording window excluding any stimulus artefact".

Unlike the last NHSP protocol, the new one uses the same noise measuring method for both establishing a "clear response" (CR) (>3:1 s/n) and establishing a "response absent" (RA) - the pair of waveforms are optimally superimposed (i.e. not simply wave V points aligned) and the average gap between them judged visually. For RA this should be no more than 25nV.