The detection of ‘virtual’ objects using echoes by humans: Spectral cues

Abstract

Some blind people use echoes to detect discrete, silent objects to support their spatial orientation/navigation, independence, safety and wellbeing. The acoustical features that people use for this are not well understood. Listening to changes in spectral shape due to the presence of an object could be important for object detection and avoidance, especially at short range, although it is currently not known whether it is possible with echolocation-related sounds. Bands of noise were convolved with recordings of binaural impulse responses of objects in an anechoic chamber to create 'virtual objects', which were analysed and played to sighted and blind listeners inexperienced in echolocation. The sounds were also manipulated to remove cues unrelated to spectral shape. Most listeners could accurately detect hard flat objects using changes in spectral shape. The useful spectral changes for object detection occurred above approximately 3 kHz, as with object localisation. However, energy in the sounds below 3 kHz was required to exploit changes in spectral shape for object detection, whereas energy below 3 kHz impaired object localisation. Further recordings showed that the spectral changes were diminished by room reverberation. While good high-frequency hearing is generally important for echolocation, the optimal echo-generating stimulus will probably depend on the task.

Human Echolocation for Target Detection Is More Accurate With Emissions Containing Higher Spectral Frequencies, and This Is Explained by Echo Intensity

“…With respect to the noise emissions, our results generally agree with those by Rowan et al. (2013 , 2017 ). Specifically, in those studies participants were more accurate in detecting or localising an object in virtual acoustic space using high-pass (>3 kHz), compared to low-pass (<3 kHz), filtered noise.…”

“…As such, our results clearly highlight the importance of high frequency emissions due to higher echo intensity, above and beyond the effects of low frequency sound as described by Rowan et al. (2013 , 2017 ).…”

“… Rowan et al. (2013 , 2017 ) found that participants’ ability to localise and detect an object in virtual acoustic space was better with noise emissions containing higher spectral frequencies. Specifically, in those studies, participants were more accurate in detecting or localising an object in virtual acoustic space using high-pass (>3 kHz), compared to low-pass (<3 kHz), filtered noise.…”

“…Yet, they also found that for object azimuth localization, the addition of low frequency sound (i.e. use of broadband noise as compared to high-pass noise only) impaired echo processing ( Rowan et al., 2013 ), while for target detection the addition of low frequency sound actually improved performance ( Rowan et al., 2017 ). Thus, even though there seems to be an advantage of high frequency sound, it is unclear to what degree this advantage persists when low spectral frequency components are present at the same time.…”

Comparing Echo-Detection and Echo-Localization in Sighted Individuals

“…Fewer studies on human echolocation have been performed using echo-localization tasks, that is, with focus on the participant’s ability to localize objects using echoes (Després et al., 2005; Dufour et al., 2005; Rice, 1969; Rowan et al., 2013, 2015, 2017; Schenkman & Jansson, 1986; Teng et al., 2012; Teng & Whitney, 2011). In studies of echo-localization, participants are typically asked for the exact position of the object (e.g., Rice, 1969; Schenkman & Jansson, 1986).…”