Diotic narrowband noises can be perceived as intracranially off center in listeners with symmetrical audiometric thresholds

The ability to localize sound sources in the horizontal plane depends on the interaural time (ITD) and level (ILD) difference. It is assumed that individuals with normal and symmetrical hearing thresholds perceive stimuli with zero ILD and ITD as fused centered auditory images, which is not always true. This study aimed to explore ILD lateralization biases in individuals with normal hearing and explain whether they can be explained byan interaural asymmetry in monaural loudness. An ILD lateralization task was performed where the ILDs ranged between ±10 dB. The stimulus was a 1-equivalent-rectangular-bandwidth narrowband noise centered at 250–8000 Hz or a wideband noise. Preliminary results showed that the participants exhibited ILD lateralization biases more often at higher frequencies and minimal bias in the wideband condition. These biases were not caused by headphones, as the transducers were reversed between testing blocks. Biases were also consistent across up to three separate testing days. A loudness balancing task showed that participants perceived stimuli as equally loud, ruling out interaural asymmetry in monaural loudness. Audiometry also confirmed the absence of hearing threshold asymmetries. Therefore, lateralization biases in individuals with normal hearing are not explained by interaural disparities in loudness perception or hearing threshold asymmetry.