Statistical aspects of the relation between binaural and monaural thresholds

The inherent advantage of binaural over monaural hearing is, according to the best determinations, some 3 dB. The average binaural threshold for groups of normal listeners, however, runs considerably more than 3 dB below the corresponding monaural values. Part of the difference is accounted for by consideration of the statistics of interaural sensitivity difference in a group of normal listeners, account being taken of the interaural correlation and the subjective error of threshold determinations. The residual discrepancy of about 1 dB at middle frequencies, and rather greater at low frequencies, is a secondary effect associated with the respective use of free-field and earphone listening in the threshold investigations.