Evaluation of binaural enhancement 1 1 2 3 Evaluation of a method for enhancing interaural level differences at low frequencies 4 5

24 A method (called binaural enhancement) for enhancing interaural level differences at 25 low frequencies, based on estimates of interaural time differences, was developed and 26 evaluated. Five conditions were compared, all using simulated hearing-aid processing: (1) 27 Linear amplification with frequency-response shaping (LIN); (2) Binaural enhancement 28 combined with linear amplification and frequency-response shaping (BE); (3) Slow-acting 29 four-channel amplitude compression with independent compression at the two ears 30 (AGC4CH); (4) Binaural enhancement combined with four-channel compression (BE31 AGC4CH); (5) Four-channel compression but with the compression gains synchronized 32 across ears (SYNC-AGC4CH). Ten hearing-impaired listeners were tested, and gains and 33 compression ratios for each listener were set to match targets prescribed by the CAM2 fitting 34 method. Stimuli were presented via headphones, using virtualization methods to simulate 35 listening in a moderately reverberant room. The intelligibility of speech at 60 azimuth in 36 the presence of competing speech on the opposite side of the head at 60 azimuth was not 37 affected by the binaural enhancement processing. Sound localization was significantly better 38 for condition BE-AGC4CH than for condition AGC4CH for a sentence, but not for broadband 39 noise, lowpass noise or lowpass amplitude-modulated noise. The results suggest that the 40 binaural enhancement processing can improve localization for sounds with distinct envelope 41 fluctuations. 42 Moore et al. Evaluation of binaural enhancement 3