Directional loudness is that phenomenon by which the loudness of a sound may vary according to the localization of its source. This phenomenon has been mainly observed for high-frequency sounds, for sources located in the horizontal plane. Because of the acoustic shadow of the head, the left and right ear pressures are modified depending on the source azimuth and the global loudness resulting from a summation process may vary accordingly. Directional loudness has also been reported to occur at 400 Hz, where shadowing effects are usually rather small. It might therefore be suspected that directional loudness effects could be influenced by other parameters involved in the localization process. This study assessed the loudness of low-frequency pure tones (200 and 400 Hz) lateralized with headphones by applying an interaural time difference (ITD) but no interaural level difference. It showed small but significant variations of loudness with respect to ITD at a low loudness level (40 phon): ITD values associated with virtual azimuths of ±60° and ±90° led to a small but significant increase in loudness (up to 1.25 dB). However, there was no such effect at a moderate loudness level (70 phon).

International audienceNavigation in virtual environments relies on an accurate spatial rendering. A virtual object is localized according to its position in the environment, which is usually defined by the following three coordinates: azimuth, elevation and distance. Even though several studies investigated the perception of auditory and visual cues in azimuth and elevation, little has been made on the distance dimension. This study aims at investigating the way humans estimate visual and auditory egocentric distances of virtual objects. Subjects were asked to estimate the egocentric distance of 2–20 m distant objects in three contexts: auditory perception alone, visual one alone, combination of both perceptions (with coherent and incoherent visual and auditory cues). Even though egocentric distance was under-estimated in all contexts, the results showed a higher influence of visual information than auditory information on the perceived distance. Specifically, the bimodal incoherent condition gave perceived distances equivalent to those in the visual-only condition only when the visual target was closer to the subject than the auditory target