Adapting the EC Model to the Frequency Dependency of Binaural Masking Level Differences – Is this Relevant for Speech in Noise?

Several binaural speech intelligibility models simulate human binaural processing using the Equalization-Cancellation (EC) mechanism, incorporating processing inaccuracies based on tone-in-noise detection at 500~Hz. Despite this, such inaccuracies are typically assumed to be frequency-independent in binaural speech intelligibility models. This study examines the validity of that assumption and explores how auditory filter bandwidth affects binaural masking release. Experiment I measured tone detection thresholds across frequencies from 250 to 2000~Hz in 12 normal-hearing and 5 hearing-impaired listeners, varying the interaural phase difference (IPD) of noise between 0 and 5$\pi$. Results were compared with EC model predictions. Binaural inaccuracies showed a low-pass effect, reducing binaural masking level differences (BMLDs) at higher frequencies. However, the EC model inaccurately predicted BMLDs at 250~Hz. Experiment II involved a subset of listeners performing speech-in-noise intelligibility tasks with low-pass filtered speech. This allowed assessment of whether tone-in-noise detection could predict speech recognition thresholds (SRTs), particularly in hearing-impaired individuals whose low-frequency hearing remained near normal. Findings revealed that adapting the model’s binaural inaccuracies improved SRT predictions beyond audiometric thresholds alone.on at 500 Hz. Despite this, such inaccuracies are typically assumed to be frequency-independent in