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Information Technologies for Visually Impaired People
Plus[8]. Using a "graphical" embosser the formulas are represented
using a mix of Braille characters and graphics, in a
way which is close to the graphical layout. Braille characters
are used to represent the basic elements, like digits and
letters, while the mathematical symbols are represented
graphically: fraction bar, square root, arithmetic operators.
Additionally this representation keeps the graphical layout
of the formula (for instance a fraction is represented by
a graphical line with the numerator above and the denominator
below).
This representation is quite interesting to help pupils to
understand the meaning of a formula, but unfortunately it is
based on paper printouts and therefore can only be used to
read, rather than to write or edit a formula.
1.4 Speech
Speaking a formula is the other option. The linear version
of the formula is said by a human speaker or by a speech
synthesiser. In this case there are some non trivial problems
of ambiguity. For instance if we consider the formula 1, it
will be naturally spoken like the following sentence: "x plus
1 over x minus 1'’. However, there are 3 other ways in which
this sentence can be understood: see formulas in Figure 4.
Another obstacle to comprehension of audio-based mathematical
information is the increase of the mental work involved
in the retention and comprehension of audio-based
mathematical information. Indeed whereas the reader can
use the printed page as the external memory and an aid to
retention, the listener has only their memory of the spoken
utterance, thus making the comprehension of syntactically
rich data extremely difficult.
Much of the investigation into the intelligibility of synthetic
speech has been carried out using lists of single words,
separated by pauses [9]. It was demonstrated that when the
length of the pause was reduced, the retention was degraded
far below that of natural speech. Waterworth conjectures
that the reason for this is that listeners are exhibiting a recency
or primacy effect [9]. It is inferred that the listener’s
working memory is concerned with either analysing and
interpreting the acoustic input, or rehearsing material which
is already present.
Coupled with this, Pisoni [10] has shown that the comprehension
of synthetic speech depends on the quality of
the system, and varies over a wide range; from 95.5% in the
case of natural speech, to 75% when poor quality synthetic
speech was in use. It can be further inferred that the intelligibility
of spoken output is determined by:
Whether the spoken output is synthetic or natural.
The quality of synthetic speech.
The level of prosody contained in the spoken utterance.
The prosodic component of speech [11] is that set of
features which lasts longer than a single speech sound. The
term prosody can be traced back to ancient Greek where it
was used to "refer to features of speech which were not
indicated in orthography, specifically to the tone or melodic
accent which characterised full words in ancient Greek’’
[12]. The term prosody remained almost forgotten until the
1940s, when it was revived as an approach to the study of
linguistic analysis.
Another major factor in the understanding of synthetic
speech is the fatigue effect which is primarily brought about
by the monotonous quality of synthetic speech. It has been
found that the introduction of prosodic cues into spoken
output has increased intelligibility significantly. One possible
reason for this is the relieving effect that the inclusion
of prosodic features, such as alterations in the pitch range,
and changes in the rate introduce a rhythm more akin to
natural speech, hence relieving the tedium of the monotonous
voice.
This fact has major implications for the presentation of
syntactically complex material such as mathematical equations.
Three sets of rules are known to exist for the production
of spoken mathematics. The first is provided by the
Confederation of Taped Information Suppliers (COTIS), the
second is a set of guidelines written by Larry Chang [13],
and the third is devised by Abraham Nemeth [14]. These
rules attempt to alleviate the problem of syntactically rich
material through the addition of lexical cues, adding to the
mental workload of the listener.
Also, both these sets of guidelines are aimed at the human
reader. Consequently, they are flexible enough to permit
the semantic interpretation of the material, or to read
the various symbols as they occur. In addition, the fact that
both sets of rules are intended for human use assumes that
the human reader can employ all features of natural speech
when speaking the material. Such semantic interpretation
is not available to any automated system; necessitating the
development of a tighter set of rules to unambiguously
present the material.
1.5 Computer Tools
During the past 3 decades, considerable progress has
been made in the field of access to information for the group
of blind and visually impaired people. Thanks to modern
information technology in the mainstream and to very specialised
adaptive and assistive technologies, blind and visually
impaired people are now able to deal independently
and efficiently with almost every piece of information that
is composed of pure text.
Despite current strong trends towards graphical presentation,
text still covers the majority of relevant contents for
private and professional life, such that information access
for this target group is currently accomplished to a very
large extent.
On the other hand, blind and visually impaired people
are still excluded from an efficient usage and handling of
graphical content. Since Mathematics is presented in a highly
graphical way most of the time, this exclusion implies considerable
restrictions in access to Mathematics.
The problems faced by the target group with respect to
Mathematics fall into four basic categories [15]:
1. Access to mathematical literature (books, teaching
materials, papers etc.).
32 UPGRADE Vol. VIII, No. 2, April 2007 © Novática