A summary of research investigating echolocation abilities of blind and sighted humans

doi:10.1016/j.heares.2014.01.010

Hearing Research

Volume 310, April 2014, Pages 60-68

https://doi.org/10.1016/j.heares.2014.01.010 Get rights and content

Highlights

•
Blind and sighted individuals can perceive objects using echolocation.
•
Cues include level, spectral envelope, emission-echo delay, and binaural differences.
•
On average, the blind are better echolocators than the sighted.
•
Visual brain areas of the blind are recruited for processing echolocation information.

Abstract

There is currently considerable interest in the consequences of loss in one sensory modality on the remaining senses. Much of this work has focused on the development of enhanced auditory abilities among blind individuals, who are often able to use sound to navigate through space. It has now been established that many blind individuals produce sound emissions and use the returning echoes to provide them with information about objects in their surroundings, in a similar manner to bats navigating in the dark. In this review, we summarize current knowledge regarding human echolocation. Some blind individuals develop remarkable echolocation abilities, and are able to assess the position, size, distance, shape, and material of objects using reflected sound waves. After training, normally sighted people are also able to use echolocation to perceive objects, and can develop abilities comparable to, but typically somewhat poorer than, those of blind people. The underlying cues and mechanisms, operable range, spatial acuity and neurological underpinnings of echolocation are described. Echolocation can result in functional real life benefits. It is possible that these benefits can be optimized via suitable training, especially among those with recently acquired blindness, but this requires further study. Areas for further research are identified.

Section snippets

Introduction and background

Adaptation to sensory loss has been the focus of considerable interest in psychology and neuroscience. Visual loss is often, although not uniformly, associated with enhanced auditory abilities, and these may be partly a consequence of cortical reorganization and recruitment of visual areas for auditory processing (Collignon et al., 2009, Voss et al., 2004, Voss et al., 2010). Many studies have examined the role that echolocation can play in improving spatial awareness for those who have lost

Characteristics of echolocation signals used by humans

Bats echolocate using biosonar: the emitted signals are mainly in the ultrasonic range, beyond the upper frequency limit of human hearing (approximately 20,000 Hz). This can provide the bat with a rich source of information about very small objects, such as insects, including size, position, and direction of movement. Many blind individuals also use self-generated sounds to echolocate, such as clicks produced by rapidly moving the tongue in the palatal area behind the teeth (Rojas et al., 2009

A summary of research comparing echolocation performance of blind and sighted participants

Echoic information provides useful information regarding the surrounding environment (Kolarik et al., 2013c, Mershon et al., 1989), and blind individuals rely heavily upon this information for perceiving the spatial layout of their surroundings. In this section, we address the issue of whether blind people have superior echolocation abilities to sighted people. Various factors may contribute to the development of superior echolocation abilities in blind people, such as reliance on and extensive

Neuronal bases of echolocation

Little is currently known regarding the neural basis of echolocation, and whether the mechanisms subserving echolocation differ between sighted and blind individuals. In addition to the evidence for enhanced echolocation by blind people (Kellogg, 1962, Rice, 1969, Schenkman and Nilsson, 2010, Schenkman and Nilsson, 2011), as described above, there is evidence that blind people display enhanced abilities for auditory tasks such as sound localization (Lessard et al., 1998, Voss et al., 2004) and

Concluding remarks and suggestions for further research

The studies described in this review have provided numerous insights into echolocation in humans. However, many aspects of echolocation are not yet understood, and the reasons for individual differences in echolocation ability have not been determined. Further work is needed to clarify what cues are used in the various aspects of echolocation, to establish the functional benefits of echolocation, to investigate the accuracy of locomotive guidance using echolocation, and to establish how the

Acknowledgments

We thank the Editor in Chief, Barbara Canlon, and an anonymous reviewer for their helpful comments that improved a previous version of the manuscript. The research was supported by MRC grant G0701870 and the Vision and Eye Research Unit (VERU), Postgraduate Medical Institute at Anglia Ruskin University.

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Ambient sound can mask acoustic signals. The current study addressed how echolocation in people is affected by masking sound, and the role played by type of sound and spatial (i.e. binaural) similarity. We also investigated the role played by blindness and long-term experience with echolocation, by testing echolocation experts, as well as blind and sighted people new to echolocation. Results were obtained in two echolocation tasks where participants listened to binaural recordings of echolocation and masking sounds, and either localized echoes in azimuth or discriminated echo audibility. Echolocation and masking sounds could be either clicks or broad band noise. An adaptive staircase method was used to adjust signal-to-noise ratios (SNRs) based on participants’ responses. When target and masker had the same binaural cues (i.e. both were monoaural sounds), people performed better (i.e. had lower SNRs) when target and masker used different types of sound (e.g. clicks in noise-masker or noise in clicks-masker), as compared to when target and masker used the same type of sound (e.g. clicks in click-, or noise in noise-masker). A very different pattern of results was observed when masker and target differed in their binaural cues, in which case people always performed better when clicks were the masker, regardless of type of emission used. Further, direct comparison between conditions with and without binaural difference revealed binaural release from masking only when clicks were used as emissions and masker, but not otherwise (i.e. when noise was used as masker or emission). This suggests that echolocation with clicks or noise may differ in their sensitivity to binaural cues. We observed the same pattern of results for echolocation experts, and blind and sighted people new to echolocation, suggesting a limited role played by long-term experience or blindness. In addition to generating novel predictions for future work, the findings also inform instruction in echolocation for people who are blind or sighted.
Utilizing gammatone filter coefficient to improve human mouth-click signal detection using a multi-phase correlation process
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This study introduces an enhanced structured signal processing scheme for detecting the “transmit-echo” of mouth-click signals used by blind individuals for echolocation. The processing scheme is based on coexisting work on the detection of the mouth-click signal, with an additional band-pass filter process introduced before synthesis, multi-phase correlation, and summation. The level of side lobes at the output was improved by more than −19 dB, and the number of local maxima was minimized by using a band-pass filter. The detection of “transmit-echo” results using artificial mouth-click signal data was validated and achieved a 100% success rate in detecting obstacles at 60 cm, 80 cm, and 100 cm. Nonetheless, the detection scheme discussed in this investigation is thought to be intuitive, having been learned from the human hearing process. The emerging concepts in this research are expected to benefit radar and sonar system applications in the near future.
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Receiving navigation directions and relevant information through appropriate channels is crucial for individuals with visual impairments when they use navigation assistant systems. Various navigation assistant systems have implemented diverse methods and modalities to provide navigation instructions to users. Moreover, several studies have examined the preferences of individuals with visual impairments regarding modalities. These studies have primarily relied on surveys or interviews to report their findings. In this study, we extensively investigated the type of navigation information individuals with visual impairments would prefer to receive. To achieve this, we employed a mixed-method design comprising an experiment, a questionnaire, and interviews conducted with participants with visual impairments and individuals with 20/20 vision who were blindfolded. We tested unimodal instruction modes (audio only) and multimodal instruction modes (audio and vibration), along with two types of audio instructions: short and descriptive. To evaluate the participants’ navigation performance, we measured the time taken and errors made during navigation using different instruction types and modes. The findings of this study suggest that the instruction mode does not have any significant effect on the time taken or errors made to complete the trials. Additionally, no evidence was found to support the preference for descriptive instructions over short instructions among the participants. Furthermore, the study did not find evidence to suggest that participants prefer receiving detailed instructions about the environment and obstacles during navigation. It became evident that participants had varying preferences for instruction modes, highlighting the importance of customized functionalities in navigation assistant systems. Moreover, our study validated that participants with visual impairments spent less time and made fewer errors during navigation compared to blindfolded participants with 20/20 vision. We believe that the results of this study will contribute to expanding the understanding of user preferences regarding the type and modality of instructions in the domain of assistive navigation technology.
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Il est d’observation très ancienne que des personnes atteintes de cécité utilisent l’audition pour se situer dans l’espace avec une précision qui leur confère une grande autonomie au quotidien même dans des lieux inconnus. Cette capacité principalement basée sur l’écholocalisation n’est pas universelle, mais elle n’est pas non plus réservée qu’aux aveugles de naissance. Réciproquement, les personnes sourdes notamment signeuses font preuve de performances visuelles périphériques dynamiques, supérieures à la norme. Les mesures en laboratoire permettent de quantifier les performances par rapport à celles d’individus sans handicap sensoriel, de confirmer leur supériorité, mais celle-ci n’est pas spectaculaire. Dans la problématique de la plasticité sensorielle, ces observations soulèvent plusieurs questions d’actualité détaillées dans la présente revue : les ressources requises sont-elles développées à partir de l’existant, c’est-à-dire présentes chez la personne non handicapée, mais peu exploitées ? Faut-il allouer des ressources computationnelles supplémentaires existantes, mais gourmandes en charge attentionnelle ? Et surtout, les situations non écologiques créées en laboratoire sont-elles adéquates pour évaluer la performance dans la vraie vie ?
It has been reported for centuries that some blind people use their hearing to guide themselves spatially with enough precision to enjoy great autonomy in daily life, even in unknown places. This ability that mainly rests on echolocation is not universal, but neither is it restricted to congenitally blind subjects. In a somewhat symmetric paradigm, deaf people, especially users of sign language, show supranormal dynamic peripheral visual performance. Laboratory measurements make it possible to quantify their performances compared to those of individuals without sensory handicap, to confirm their superiority but the findings are not spectacular. In the issue of sensory plasticity, these observations raise several currently open issues detailed in this review: are the required resources developed from already existing abilities, that is, present but little used in non-disabled persons? Should existing additional computational resources be allocated at the expense of increased cognitive load? And above all, are the non-ecological situations created in the laboratory adequate for evaluating performance in real life?
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ReviewA summary of research investigating echolocation abilities of blind and sighted humans

Highlights

Abstract

Section snippets

Introduction and background

Characteristics of echolocation signals used by humans

A summary of research comparing echolocation performance of blind and sighted participants

Neuronal bases of echolocation

Concluding remarks and suggestions for further research

Acknowledgments

Appl. Acoust.

Neuropsychologia

Brain Res.

Brain Res.

Hum. Mov. Sci.

Neuropsychologia

Neuropsychologia

Biomed. Signal Process.

Hear. Res.

Curr. Biol.

Acoustic waveform inversion with application to seasonal snow covers

J. Acoust. Soc. Am.

“Facial vision”: the perception of obstacles out of doors by blindfolded and blindfolded-deafened subjects

Am. J. Psychol.

Auditory perception of walls via spectral variations in the ambient sound field

J. Rehabil. Res. Dev.

Obstacle perception by congenitally blind children

Percept. Psychophys.

Insights into dolphin sonar discrimination capabilities from human listening experiments

J. Acoust. Soc. Am.

Repetition pitch: monaural interaction of a sound with the repetition of the same, but phase shifted sound

Acustica

The use of echolocation as a mobility aid for blind persons

J. Vis. Impair. Blind

The role of the sound of tapping for nonvisual judgment of gap crossability

J. Exp. Psychol. Hum. Percept. Perform.

The auditory skills necessary for echolocation: a new explanation

J. Vis. Impair. Blind

Obstacle detection with and without the aid of a directional noise generator

Am. Found. Blind Res. Bull.

Cross-modal plasticity for the spatial processing of sounds in visually deprived subjects

Exp. Brain Res.

“Facial vision:” the role of pitch and loudness in the perception of obstacles by the blind

Am. J. Psychol.

Echo features used by human listeners to discriminate among objects that vary in material or wall thickness: implications for echolocating dolphins

J. Acoust. Soc. Am.

Blind subjects process auditory spectral cues more efficiently than sighted individuals

Exp. Brain Res.

Enhanced sensitivity to echo cues in blind subjects

Exp. Brain Res.

Echolocation by blind men, bats and radar

Science

Echo perception of shape and texture by sighted subjects

Percept. Mot. Ski.

Contributions to a Psychology of Blindness

Sensory compensation in sound localization in people with one eye

Exp. Brain Res.

Echolocation

Curr. Biol.

Diderot's Early Philosophical Works

The role of audition and motion in the spatial orientation of the blind and the sighted

Scand. J. Psychol.

Sonar system of the blind

Science

Visual acuity and its measurement

Ophthalmol. Clin. North Am.

Orientation by aural clues

Am. Found. Blind Res. Bull.

Evidence for enhanced discrimination of virtual auditory distance among blind listeners using level and direct-to-reverberant cues

Exp. Brain Res.

Discrimination of virtual auditory distance using level and direct-to-reverberant ratio cues

J. Acoust. Soc. Am.

Using acoustic information to perceive room size: effects of blindness, room reverberation time, and stimulus

Perception

Sensory substitution information informs locomotor adjustments when walking through apertures

Exp. Brain Res.

Neuronal representations of distance in human auditory cortex

Proc. Natl. Acad. Sci. U. S. A.

Review
A summary of research investigating echolocation abilities of blind and sighted humans