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

Localizing sound sources in the horizontal plane depends on the interaural time (ITD) and level (ILD) differences. It is assumed that individuals with normal and symmetrical hearing thresholds perceive stimuli with zero ILD and ITD as fused and 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 by an interaural asymmetry in monaural loudness. An ILD lateralization task was performed where the ILDs ranged between ±20 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 across all test frequencies. These biases were not caused by headphone placement, as the transducers were reversed between testing blocks. Biases were consistent across three separate testing days. A loudness balancing task showed that participants demonstrated loudness perception imbalances across testing frequencies, which were also consistent across three separate testing days. Audiometry showed ≤10 dB hearing thresholds asymmetry. ILD lateralization biases in individuals with normal hearing were not explained by interaural asymmetries in loudness perception or hearing thresholds.