Learning Auditory Space: Generalization and Long-Term Effects

Abstract

BackgroundPrevious findings have shown that humans can learn to localize with altered auditory space cues. Here we analyze such learning processes and their effects up to one month on both localization accuracy and sound externalization. Subjects were trained and retested, focusing on the effects of stimulus type in learning, stimulus type in localization, stimulus position, previous experience, externalization levels, and time.MethodWe trained listeners in azimuth and elevation discrimination in two experiments. Half participated in the azimuth experiment first and half in the elevation first. In each experiment, half were trained in speech sounds and half in white noise. Retests were performed at several time intervals: just after training and one hour, one day, one week and one month later. In a control condition, we tested the effect of systematic retesting over time with post-tests only after training and either one day, one week, or one month later.ResultsWith training all participants lowered their localization errors. This benefit was still present one month after training. Participants were more accurate in the second training phase, revealing an effect of previous experience on a different task. Training with white noise led to better results than training with speech sounds. Moreover, the training benefit generalized to untrained stimulus-position pairs. Throughout the post-tests externalization levels increased. In the control condition the long-term localization improvement was not lower without additional contact with the trained sounds, but externalization levels were lower.ConclusionOur findings suggest that humans adapt easily to altered auditory space cues and that such adaptation spreads to untrained positions and sound types. We propose that such learning depends on all available cues, but each cue type might be learned and retrieved differently. The process of localization learning is global, not limited to stimulus-position pairs, and it differs from externalization processes.

Short-term effects of sound localization training in virtual reality

“…Typically, such adaptation has been measured over the course of hours, days and weeks (for a review see Mendonça et al 19 ). In agreement with the few studies that have also focused on short-term changes, we show that significant changes occur after a total training duration of the order of an hour spaced over three days 20,[22][23][24]37 . This is an encouraging result if future systems using generic, non-individualized HRTFs are to find broader application, since it seems likely only a minority of use cases will justify longer adaptation periods.…”

“…The possibility of accelerating the process of adapting to "new ears" has therefore received some attention. Encouragingly, several studies have demonstrated that training through positional feedback (for example, indication of virtual sound source location using visual or somatosensory cues) has the potential to achieve adaptation over timescales of the order of a few hours or even minutes [20][21][22][23][24] . Whilst it seems clear that explicit training can result in better outcomes in virtual audio, whether measured by localization accuracy or perceived externalization, improvements over short timescales are typically small and highly variable.…”

The effect of musical expertise on the representation of space

“…White noise has been previously used as a control auditory stimulus (e.g., Ishihara et al, 2013; Mendonça et al, 2013). Although all frequencies are equally represented in white noise, the sound is perceived as higher-pitched to human observers, partly because the perception of pitch is not linear, and partly because human ears are more sensitive to higher frequencies (Plack, 2005).…”

Influence of the Quality of Consumer Headphones in the Perception of Spatial Audio

“…A more specific study of spatial attributes is then necessary to better evaluate the performing of the different headphones. In this direction, the localization accuracy in azimuth is one of the most studied spatial attributes [22][23][24][25] and therefore a good anchor point to contrast the previous Test 2 with a localization experiment. Therefore, this test tries to establish a relation of the influence of the frequency response on the azimuth localization in the horizontal plane.…”