Detection, thresholds of human echolocation in static situations for distance, pitch, loudness and sharpness

Human echolocation describes how people, often blind, use reflected sounds to obtain information abouttheir ambient world. Using auditory models for three perceptual variables, loudness, pitch and one aspectof timbre, namely sharpness, we determined how these variables can make people detect objects byecholocation. We used acoustic recordings and the resulting perceptual data from a previous study withstationary situations, as input to our analysis. One part of the analysis was on the physical room acousticsof the sounds, i.e. sound pressure level, autocorrelation and spectral centroid. In a second part we usedauditory models to analyze echolocation resulting from the perceptual variables loudness, pitch andsharpness. Based on these results, a third part was the calculation of psychophysical thresholds with anon-parametric method for detecting a reflecting object with constant physical size for distance, loud-ness, pitch and sharpness. Difference thresholds were calculated for the psychophysical variables, sincea 2-Alternative-Forced-Choice Paradigm had originally been used. We determined (1) detection thresh-olds based on repetition pitch, loudness and sharpness varied and their dependency on room acousticsand type of sound stimuli. We found (2) that repetition pitch was useful for detection at shorter distancesand was determined from the peaks in the temporal profile of the autocorrelation function, (3) loudnessat shorter distances provides echolocation information, (4) at longer distances, timbre aspects, such assharpness, might be used to detect objects. (5) It is suggested that blind persons may detect objects atlower values for loudness, pitch strength and sharpness and at further distances than sighted persons.We also discuss the auditory model approach. Autocorrelation was assumed as a proper measure forpitch, but we ask whether a mechanism based on strobe integration is a viable possibility.Ytterligare forskningsfinansiär: Promobilia, projektnummer 12006 och 18003, QC 20200525