Amount of noise in (the recognisable definition of) an ERP
Averaging does not perfectly remove the noise. Assuming the signal is perfectly correlated across repetitions/sweeps/trials and the noise is independent, than doing from 1 to 2 sweeps will increase the SNR by 3 dB (i.e., decrease the noise by 1/2), Every doubling in the number of sweeps increases the SNR by 3 dB so that after 1024 sweeps the SNR has improved by at most 30 dB. This means that after averaging there is a minimum magnitude required for a peak/notch to be considered statistically reliable. Any ripples with smaller magnitudes are ignored since they are not statistically reliable.