Relearning Auditory Spectral Cues for Locations Inside and Outside the Visual Field

Abstract

Previous research has demonstrated that, over a period of weeks, the auditory system accommodates to changes in the monaural spectral cues for sound locations within the frontal region of space. We were interested to determine if similar accommodation could occur for locations in the posterior regions of space, i.e. in the absence of contemporaneous visual information that indicates any mismatch between the perceived and actual location of a sound source. To distort the normal spectral cues to sound location, eight listeners wore small moulds in each ear. HRTF recordings confirmed that while the moulds substantially altered the monaural spectral cues, sufficient residual cues were retained to provide a basis for relearning. Compared to control measures, sound localization performance initially decreased significantly, with a sevenfold increase in front-back confusions and elevation errors more than doubled. Subjects wore the moulds continuously for a period of up to 60 days (median 38 days), over which time performance improved but remained significantly poorer than control levels. Sound localization performance for frontal locations (audio-visual field) was compared with that for posterior space (audio-only field), and there was no significant difference between regions in either the extent or rate of accommodation. This suggests a common mechanism for both regions of space that does not rely on contemporaneous visual information as a teacher signal for recalibration of the auditory system to modified spectral cues.

Acoustic analysis of the directional information captured by five different hearing aid styles

“…Previous work has demonstrated that listeners are able to recalibrate to new HRTFs following a relatively prolonged period of exposure Carlile et al, 2007;Carlile and Blackman, 2014;Majdak et al, 2013). Presumably the quality of that spatial information will be dependent on both the extent of the locationdependent changes and the uniqueness of the spectral profiles for each location.…”

“…Previous studies have also demonstrated that when ear molds are worn continuously over a period of many days (10-60 days), subjects adapt to different degrees to the distorted HRTFs for spatial locations both within and outside the visual field (Carlile et al, 2007;Carlile and Blackman, 2014). These inter-subject differences in the time taken to adapt and the extent of the adaptation remain unexplained.…”

“…This monaural filtering, described by the head related transfer function (HRTF), is dependent on the precise morphology of the outer ear Teranishi and Shaw, 1968;Shaw, 1974a,b). Changes to the shape of the ear by say, partially filling the ear with a mold, produce acoustically and perceptually significant changes in the filtering Hofman and Van Opstal, 2003;Carlile et al, 2007;Carlile and Blackman, 2014).…”

Accommodating to new ears: The effects of sensory and sensory-motor feedback

“…A number of more recent studies have examined the functional plasticity of the adult auditory system when localization cues are perturbed (ferrets: Kacelnik et al, 2006;humans: Van Wanrooij and Van Opstal, 2007;Kumpik et al, 2010;Carlile and Blackman, 2013; see also owls: Knudsen et al, 1994). Human subjects have also been shown to accommodate to some extent to perturbation of the monaural spectral cues in one ear only (Van Wanrooij and Van Opstal, 2005).…”

The effect of velocity on auditory representational momentum

“…12 To generate moving VAS stimuli, broadband noise (300 Hz to 16 kHz, 5 ms cosine ramps) was convolved with the transfer functions for successive horizontal positions (e.g., see Ref. 13).…”