Below is the result of my scanning an article that appeared earlier this
year in the Journal of the Acoustical Society of America, whose source (a
talk last December at an ASA meeting) is indicated at the bottom.

--Nelson Blachman
  Oakland, Calif.
___________
Ultrasonic Eyeglasses for the Blind

hy Leslie Kay

ilion substitution has been long-sought-after as
a means for enabling blind persons to be more
 Ni effectively rehabilitated, and for young blind
children to develop more naturally like sighted children.
Animals such as the bat have developed sonar methods for
very effectively finding their way in the darle and catching
food. The same is truc for dolphins who use their sonar
system underwater. These skills have often been quoted as
good reasons to think that an "air-sonar" device might
greatly help the blind, but for many years no one had the
thought of developing an air-sonar as a "vision substitute:"
But the development of sonic eyeglasses in the early 1970's
changed our thinking.
 For the next 20 years a sensor system was under deve1--
opment to further improve the ability of, users to perceive
their surroundings. In the maritime, the sonic eyeglasses
became widely used. The stage has now been reached when
blind persons can walk about like sighted persons in a busy
shopping area going in and out of shops, and be able to
recognize their location relative to the many landmarks on
the way. We are calling the new process "sonocular per-
ception" - or seeing with round. Blind persons appear to
look at where they are going, and they can focus their at-
tention on specific objects like sighted persons fixate on
objects so as better to recognize them.
 An example of sonar eyeglasses is illustrated in the back-
ground figure. These were specially developed for a blind
child. There are three sensing elements: one radiates ultra-
sonic waves, and the other two act as reeeivers. Figure 1
shows a newer sensor (known as KASPA) fitted in a head
band that has, in addition, a central field of view modeling
the function of the eye's fovea. The fovea is a retinal crea
producing focused vision and containing the photorecep-
tors that enable color vision. The sensor has greater spatial
resolution by a factor of 6 than is available with the eyeglasses.
 The vision substitution method produces ultrasonic wave
transmission finto a wide field of view, from which a multi-

plicity of echoes is produced by each object in this field.
An object such as a bush will produce tiny echoes from the
leaves and the branches. These scattered echoes are then
received by the sonar sensing elements and are each con-
verted finto tones that have a pitch (or frequency) repre-
senting the distance to each leaf.
 We call these multiple tones a `tone complex,' and the
round that is heard through miniature earphones by a user
is called a `sound signature.' With the sensor mounted on
the forehead and moved about in a looking action, a blind
user senses in a stereophonic form, the multiple object space
that malees up the eüvironment in which movement takes
place.
 The remarkabie auditory experience one gets when lirst
trying the vision substitute is the real-time change in sound
that takes place as the head mover. This is because of the
resulting change in view of the objects. This is like normal
sight, but we pay no attention to the constant change. In-
deed, the brain converts optical images at the eye, as they
change with view, finto invariant objects as leen from a dif-
ferent angle.
 An experienced blind user of sonocular perception finds
that the brain does similar things to the sound signatures.
Each object is located and recognized as a separate entity.
But this of course is not with the clarity of optical vision.
Only those blind users who have developed the ability over
time come to say that this is their experience.
 Sighted persons have not had a need to spend the time
learning to lee with round. For those blind persons who
have, some quite remarkable skills have been developed.
For example, some blind persons have learned to cycle in
slalom fashion between a row of pules spaced 2 meters
apart just as in snow sküng. A totally blind young man
using a softball bat has shown that he can hit, with a good
whack, a softball that is thrown at him. These examples
were thought to be "not possible." This is especially so in

oonünued on page 5

Figure I.
Sensor
fitted in a
head hand.

 the case of hitting a ball because the bio-acoustic vision
substitution eyeglasses must provide information of the tra-
jectory of the ball and the brain must interpret this in real-
time if contad is to be nade at the appropriate moment.
The bio-acoustic mechanism is not yet fully understood.
We do know however, that the acoustic flow that is gener-
ated by the echo from the ball is rich in spatial information.

 Le.slie Kav is a reseczrcher ai Spatial Sensirtg Labnrcttory,
Bay Advarzced Technologies Lid., PO. Box 724. Russell, New
Zealand. This is u lay-language version of a Di.stin,yui,shed
Lectura presentad December 5 ai the 140th ASA meeting ai
Newport Beach, reprinted with the author's perznis.sinn.


VICUG-L is the Visually Impaired Computer User Group List.
To join or leave the list, send a message to
[log in to unmask]  In the body of the message, simply type
"subscribe vicug-l" or "unsubscribe vicug-l" without the quotations.
 VICUG-L is archived on the World Wide Web at
http://maelstrom.stjohns.edu/archives/vicug-l.html