Head-related transfer functions (HRTFs) capture the direction-dependant way that sound interacts with the head and torso. In virtual audio systems, which aim to emulate these effects, non-individualized, generic HRTFs are typically used leading to an inaccurate perception of virtual sound location. Training has the potential to exploit the brain’s ability to adapt to these unfamiliar cues. In this study, three virtual sound localization training paradigms were evaluated; one provided simple visual positional confirmation of sound source location, a second introduced game design elements (“gamification”) and a final version additionally utilized head-tracking to provide listeners with experience of relative sound source motion (“active listening”). The results demonstrate a significant effect of training after a small number of short (12-minute) training sessions, which is retained across multiple days. Gamification alone had no significant effect on the efficacy of the training, but active listening resulted in a significantly greater improvements in localization accuracy. In general, improvements in virtual sound localization following training generalized to a second set of non-individualized HRTFs, although some HRTF-specific changes were observed in polar angle judgement for the active listening group. The implications of this on the putative mechanisms of the adaptation process are discussed.

No abstract

Head-related transfer functions (HRTFs) capture the direction-dependant way that sound interacts with the head and torso. In virtual audio systems, which aim to emulate these effects, non-individualized, generic HRTFs are typically used leading to an inaccurate perception of virtual sound location. Training has the potential to exploit the brain’s ability to adapt to these unfamiliar cues. In this study, three virtual sound localization training paradigms were evaluated; one provided simple visual positional confirmation of sound source location, a second introduced game design elements (“gamification”) and a final version additionally utilized head-tracking to provide listeners with experience of relative sound source motion (“active listening”). The results demonstrate a significant effect of training after a small number of short (12-minute) training sessions, which is retained across multiple days. Gamification alone had no significant effect on the efficacy of the training, but active listening resulted in a significantly greater improvements in localization accuracy. In general, improvements in virtual sound localization following training generalized to a second set of non-individualized HRTFs, although some HRTF-specific changes were observed in polar angle judgement for the active listening group. The implications of this on the putative mechanisms of the adaptation process are discussed.

No abstract

The computation of binaural cues such as the Interaural Time Difference (ITD) and Interaural Level Difference (ILD) by the auditory system is known to play an important role in spatial hearing. It is not yet understood how such computations are performed in realistic acoustic environments where noise and reverberations are present. It has been hypothesized that robust sound localization is achieved through the extraction of the ITD information in the rising part of amplitude modulated (AM) sounds. Dietz et al. (2013) tested this hypothesis using psychoacoustics and MEG experiments. They presented AM sounds with ITDs varying during the course of one AM cycle. Their results showed that participants preferentially extracted the ITD information in the rising portion of the AM cycle. We designed a computational model of the auditory pathway to investigate the neural mechanisms involved in this process. Two mechanisms were tested. The first one corresponds to the adaptation in the auditory nerve fibers. The second mechanism occurs after coincidence detection and involves a winner-take-all network of ITD sensitive neurons. Both mechanisms qualitatively accounted for the data, consequently we suggest further experiments based on similar stimuli to distinguish between the two mechanisms. Dietz et al. (2013), “Emphasis of spatial cues in the temporal fine structure during the rising segments of amplitude-modulated sounds,” Proc. Natl. Acad. Sci. 110(37), 15151-15156.

Sound localization in reverberant environments is a difficult task that human listeners perform effortlessly. Many neural mechanisms have been proposed to account for this behavior. Generally they rely on emphasizing localization information at the onset of the incoming sound while discarding localization cues that arrive later. We modelled several of these mechanisms using neural circuits commonly found in the brain and tested their performance in the context of experiments showing that, in the dominant frequency region for sound localisation, we have a preference for auditory cues arriving during the rising slope of the sound energy (Dietz et al., 2013). We found that both single cell mechanisms (onset and adaptation) and population mechanisms (lateral inhibition) were easily able to reproduce the results across a very wide range of parameter settings. This suggests that sound localization in reverberant environments may not require specialised mechanisms specific to that task, but may instead rely on common neural circuits in the brain. This is in line with the theory that the brain consists of functionally overlapping general purpose mechanisms rather than a collection of mechanisms each highly specialised to specific tasks. This research is fully reproducible, and we made our code available to edit and run online via interactive live notebooks.