Instrumentation & Measurement Magazine 23-4 - 14

An Electronic Travel Aid Device to
Help Blind People Playing Sport
Sylvain Ferrand, François Alouges, and Matthieu Aussal

lind people can locate and track a sound source with
remarkable efficiency. Following this principle, we
have developed an autonomous embedded device
capable of guiding people using a spatialized virtual sound
source. In this device, we use both the information provided by
an accurate and low-latency real-time location system (RTLS)
and the head orientation data provided by a low-cost inertial
unit (IMU) to produce in real-time spatialized sound by binaural filtering. The system described in this paper has been
designed to minimize the overall latency for both the location
system and the binaural audio rendering engine. It demonstrates that it is possible to guide people by tracking spatial
sound accurately, naturally, and with minimal training.

Introduction to Electronic Travel Aid
Devices
Visual impairment is a prevalent disability that strongly affects
people's autonomy. Indeed, 216 million people are visually
impaired in the world while 36 million people are completely
blind [1]. Conventional aids, such as white canes or guide
dogs, help these people have more autonomy in their movements. However, these traditional means remain limited.
Indeed, while the white cane gives information confined to the
immediate environment, the dog can perform more complex
tasks but still with very limited navigation planning capabilities. Electronic Travel Aid (ETA) devices have thus been
developed to overcome these shortcomings.
ETA devices already have a long history. At the end of the
19th century, the polish researcher Kazimierz Noiszewski built
a device [2] using a photoelectric cell that allowed blind people
to distinguish light from darkness by varying the intensity of a
sound. In 1912, d'Albe built the exploring Optophone [2], working on the same principle. Unfortunately, providing this kind
of information to blind people is of little use, and much later,
some systems have tried to convert complete images into tactile [3] or audio stimuli [2], [4].
Most of these projects can be classified among the Sensory
Substitution Devices (SSD), a concept that was introduced 50
years ago by Bach-y-Rita [3]. The general idea is to transmit
14

data through a different sensory channel than the one usually
used, for example, by replacing visual information with sound
encoding.
In general, different approaches to SSD can be distinguished (notice that some projects use several techniques
simultaneously):
1. Direct scene representation: It was the first approach to
SSD. It consists in trying to convert a whole visual scene
into another sensory channel. The first device of this type
[3] constituted electro-tactile actuators fixed on the back
of a person giving a representation of an image filmed
by a camera.
2. Environment analysis for scene description and obstacle avoidance: These devices sense the environment to
extract useful information for the user. Some of them
use laser sensors, for instance, the electronic white
cane by Farcy et al. [5]. Others are based on computer
vision technology as in Johnson and Higgins' obstacle avoidance device [6] which provides vibrotactile
stimuli [6] or Bujacz et al. device [7] with sonification
techniques.
3. Navigation devices focusing on guidance along a
planned path: While devices in (1) try to provide a
full representation of the environment by sensory
substitution and (2) give more parsimonious pieces
of information, helping to understand the local environment, the third method consists in giving only
information about the direction to follow. This approach
significantly reduces the amount of information to be
conveyed and then facilitates the interaction with the
user, improving the speed of information perception
and reducing the cognitive load. This approach was first
explored by Loomis [8] with a Text to Speech interface and
later with binaural stimuli [9].
Even if many SSD devices for environment representation have been developed in the past 50 years (see [10] for a
complete review on tactile SSD), very few devices are used in
practice by blind people. Major disadvantages of these techniques are: they are uncomfortable and have pervasive aspects

IEEE Instrumentation & Measurement Magazine
1094-6969/20/$25.00©2020IEEE

June 2020

Instrumentation & Measurement Magazine 23-4

Table of Contents for the Digital Edition of Instrumentation & Measurement Magazine 23-4