Hear me Flying! Does Visual Impairment Improve Auditory Display Usability during a Simulated Flight?

Abstract

Sonification refers to systems that convey information into the non-speech audio modality [1]. This technique has been largely invested in developing guidance systems for visually impaired individuals. In 2008, more than 140 systems of this type used in various application areas were referenced [2]. In aeronautics, such a system –namely the Sound Flyer– is currently used by visually impaired pilots in real flight context to control the aircraft attitude. However, it is unclear if this system would be acceptable for sighted individuals. Indeed, early visual deprivation leads to compensatory mechanisms which often result in better auditory attentional skills [7,8]. In the present study we assessed this issue. Two groups of pilots (blind vs. sighted) took part in a flight simulator experiment. They were all blindfolded to avoid potential visual information acquisition (i.e. some blind individuals had residual visual capacities). Participants had to perform successive aircraft maneuvers on the sole basis of auditory information provided by the sound flyer. Maneuvers difficulty varied with the number of parameters to apply: easy (none), medium (one: pitch or bank) or hard (two: pitch and bank). The Sound Flyer generated a pure tone (53dB SPL) modulated as a function of pitch (tonal variation) and bank (inter-aural and rhythmic variations). We assessed flight performance along with subjective (NASA-TLX) and neurological (irrelevant auditory-probe technique; [9]) measures of cognitive workload. We hypothesized that the automatic cerebral reaction to deviant auditory stimuli (10% “ti” among 90% “ta”; 56db SPL) would be affected by the difficulty [10,11] and participants’ auditory attention. Preliminary data analyses revealed that blind and sighted participants reached target-attitudes with good accuracy (mean error of 2.04°). Globally, subjective cognitive workload and brain responses to the auditory probe were influenced by the difficulty of the maneuver but not by the visual impairment. These initial results provide evidence that auditory displays are effective, not only for maintaining straight and level flight [6], but also for attaining precise aircraft attitudes. Results also suggest that flight maneuvers should remain quite simple to avoid too high cognitive workload. In other words, attitude sonification can provide robust information and, along with Brungart and Simpson [3] specifications, could contribute to the fight against spatial disorientation in the cockpit.