How broadband speech may avoid neural firing rate saturation at high intensities and maintain intelligibility

Three experiments examined the intelligibility enhancement produced when noise bands flank high intensity rectangular band speech. When white noise flankers were added to the speech individually at a low spectrum level (-30 dB relative to the speech) only the higher frequency flanker produced a significant intelligibility increase (i.e., recovery from intelligibility rollover). However, the lower-frequency flanking noise did produce an equivalent intelligibility increase when its spectrum level was increased by 10 dB. This asymmetrical intensity requirement, and other results, support previous suggestions that intelligibility loss at high intensities is reduced by lateral inhibition in the cochlear nuclei.