A special place into assistive technologies is taken up by the speech recognition and speech synthesizer, which can be used by many different users, persons with visual, language or mobility disabilities. For many years soft developers have been concerned by speech recognition and text-to-speech because we assist to great changes in informatics area and accessibility is the main condition in the creation of assistive software applications.speech recognition, text-to-speech, assistive technologies, accessibility

Ion SMEUREANU

Narcisa ISAILA

English

Research Papers in Economics

 Revista Informatica Economică nr. 2(46)/2008 
 
135
Assistive Technologies 
 
Ion SMEUREANU, Narcisa ISĂILĂ  
Academy of Economic Studies, Bucharest 
smeurean@ase.ro, isaila_narcisa@yahoo.com  
 
A special place into assistive technologies is taken up by the speech recognition and 
speech synthesizer, which can be used by many different users, persons with visual, language 
or mobility disabilities. For many years soft developers have been concerned by speech rec-
ognition and text-to-speech because we assist to great changes in informatics area and acces-
sibility is the main condition in the creation of assistive software applications. 
Keywords : speech recognition, text-to-speech, assistive technologies, accessibility. 
 
ntroduction 
Over a decade, the computer asserts one-
self as a needful instrument for persons with 
disabilities offering them a new perspective, 
a new way to live.  
For these users, the products which have ex-
isted on the market offer additional accessi-
bility to computer and are created for each 
type of disability. For example, assistive 
technology for visual disability persons in-
cludes the following products: screen enlarg-
ers, screen readers, screen review utility, 
speech recognition systems, speech synthe-
sizer, refreshable Braille displays, Braille 
embossers, text readers, word prediction pro-
grams. Assistive products for persons with 
mobility disabilities include speech recogni-
tion systems, editing programs on screen us-
ing alternative products (sip and puff, sticks, 
joysticks, trackballs), alternative keyboards, 
keyboard filters for editing or touch screens. 
The persons with learning impairments can 
use word prediction programs, reading com-
prehension programs, speech synthesizers, 
speech recognition programs. 
Many accessibility characteristics are offered 
by Windows operating system or Office 
package, which render easy the access to dif-
ferent elements using keyboard or mouse. In-
to operating system it’s remarkable the ac-
cessibility offered by Magnifier utility (for 
increasing the zoom of some screen parts), 
Screen Review (which reads information 
from screen using the sound), Narrator (for 
helping the user who works with programs 
from Control Panel, NotePad, WordPad or 
Internet Explorer browser). There are a lot of 
settings in Control Panel using Accessibility 
Options application regarding contrast, filter 
options, colors or navigation, all to increase 
accessibility to each element of application 
used by the user. 
Office package includes accessibility charac-
teristics as: zoom, contrast between graphic 
elements, the possibility to page setup for 
better seeing documents’ content (using 
Reading Layout), development accessibility 
Web pages (Microsoft FrontPage) by adding 
text to images, formatting styles, making im-
age maps. 
 
1. Speech Recognition Systems 
Named also voice recognition programs, may 
let users to introduce data, using voice in-
stead keyboard or mouse. 
The main characteristics of the speech recog-
nition system are: 
- vocabulary’s size, the number of words 
recognized  
- the separated or continuous speech 
- the conditions of noise 
- the number of speakers 
- the percentage of recognize 
- processing time, on-line, delay, off-line 
- the area of applicability 
The speech recognition is a complex process 
composed by difficult constructive parts, in 
which a part of the system, the physics part, 
converts the sound into electric signal and 
adjusts it for entrance into the next part. The 
second part, the logic part, is represented by 
the computer with sound board and necessary 
program for all required processes.  
I Revista Informatica Economică nr. 2(46)/2008 
 
136
 
AMP 
FTJ 
CAN 
Pre-processing 
Extract the 
parameters  Coding Recognize 
Database  Database 
Acoustic 
signal 
Unit 
recognized
Electro Analysis  Symbolic 
tact
Digital 
Analyse 
Fig.1. General structure of a speech recognition system 
 
For understanding human speaking, each 
speech recognition system uses four main 
components with strong connection: 
1)  Dividing text in words, process used by 
speech recognition engine, which assures 
greater or less accuracy in speech recogni-
tion. Thus: 
a)  digitization of the speech, meaning to in-
sert short pauses after each pronounced word, 
which assures finding by the system the be-
ginning and the end of the word. The advan-
tage is a little power calculation but the sys-
tem becomes unused if we don’t respect 
pauses between words. 
b)  identifying words into vocabulary me-
thod, which allows the user to speak natural-
ly without pauses between words, but the 
system can read wrong if some used words 
aren’t into the vocabulary. 
c)  continuous speaking method, offers the 
best accuracy in speech recognition 
processing every pronounced word. Because 
the system doesn’t use elements to separate 
words is necessary a longer period of time to 
find the beginning and the end for every 
word. 
2)  The vocabulary or words list, which 
speech recognition system can find to a cer-
tain moment. Using a rich vocabulary, that 
means to improve speech recognition but to 
increase the size vocabulary isn’t a guaranty 
for a better accuracy if many words have the 
same meaning. 
3)  Finding words means to search in vocal 
database and to achieve connections to each 
other and write the audio signal. 
There are two methods: 
a)  identifying the whole word, a method 
which consists in finding into the database 
for the word fit to the audio signal. That 
means less search ways but it is necessary to 
exist into the system templates for every 
word, which overload utilization. 
b)  finding phonemes into the dictionary for 
the speaker language. The advantage is a re-
duced space for keeping information but the 
disadvantage is increased by the power cal-
culation. 
4)  Dependence of the speaker is the main 
element to design and implement speech rec-
ognition system. The system can be: 
a)  independent by speaker and in this case 
there is a great resources consumption to 
convert all into dialect human speech. 
b)  dependent by speaker, using minimum 
resources but they require to educate systems 
for a few hours and so accuracy is ninety 
percentage. The users with mobility disabili-
ties prefer these systems because they are 
easily to use. 
c)  adjusted to speaker, meaning to educate 
system for the same speaker. 
The speech recognition system must achieve 
an equilibrium among four elements and to 
assure independence by characteristics of 
voice users. 
 
2. Text-to- speech (TTS) 
Starting from a written text it suppose differ-
ent constrains regarding vocabulary (theoret-
ically unlimited) but pronounced sentences 
must be as naturally respecting an usual into-
nation. Because sentences can’t be memo-
rized, it’s necessary to choose a limited en- Revista Informatica Economică nr. 2(46)/2008 
 
137
semble of linguistic units which by the 
process of concatenate allows the vocal syn-
thesis from written text. 
A text-to-speech system contains two units: 
1. a unit regarding editing text, which makes 
all the operations meaning content analyze to 
convert text in audio codes. 
2. a synthesizer, which contents hardware 
support for synthesis proceeding. 
To create and use the rules for convert text 
into vocal signal are analyzed the following 
elements: 
a)  the phonemes (sound’s parts which com-
pose the words) used to produce compute-
rized voice ; 
b)  the quality of vocal signal which depends 
on the rules of finding and converting the 
text to audio signal; intonation, emotions and 
some problems in pronunciation overload 
producing vocal signal. To eliminate these 
impediments it can be used tags control or 
associate transcription text version to tran-
scription phonetics word. 
c)  text-to-speech through concatenate di-
phones ; 
d)  using phonemes pairs to produce each 
sound. 
It’s evaluated every word and then the sys-
tem joins phonemes to pronounce the word. 
The system which concatenates diphones is 
individual language because phonemes are 
differentiated by speaker’s language. 
   
Text pre-processing  Phonemes set 
Text in ASCII format
Conversion 
graphemes- phonemes 
Conversion rules  
grapheme- phoneme 
Prosodic effects 
preparation
Phoneme to diphone 
conversion
Prosodic effects Diphones 
database 
Intonation rules 
Parameter to 
synthesizer
Hardware synthesizer   Vocal signal 
 
Fig.2. Elements of TTS system for Romanian language 
 
Speech synthesizers are the highest level of 
text-to-speech systems. They make the same 
thing as text-to-speech but there are the fol-
lowing parameters sets: 
- source characteristics: basic frequency, vo-
lume, intensity 
- acoustic characteristics of voice:  the fre-
quencies of high sonority, the band-pass 
width, the coefficients of prediction, the 
energy of the signals in of the filters. 
MBROLA is an example for the speech syn-
thesizer, which converts the text to sound us-
ing phonemes dictionary of Romanian lan-
guage. 
There are applied different accessibility tech-
nologies to make speech recognition and 
text-to-speech. Revista Informatica Economică nr. 2(46)/2008 
 
138
Sequence 
parameters 
generation 
Text  Concepts
(or)
Synthesizer
 
; Speech
 
Fig.3. Difference between TTS system and speech synthesizer 
 
3. SAPI Model (Speech Application Pro-
gramming Interface) 
Specific to Windows operating system al-
lows speech recognition and conversion of 
the text in vocal signal. SAPI is used as in-
terfaces COM (Component Object Model) 
and contents two distinctive levels: 
- high SAPI, which allows the access to 
basic services of speech recognition by 
Voice Command Object and simple out-
puts text-to-speech through Voice Text ob-
ject; 
- low SAPI, which offers large access to 
Windows speech recognition services by 
SR Engine Enumerator Objects meaning 
SR Sharing and conversion of the text in 
vocal signal through TTS Enumerator and 
TTS Engine Objects. 
Low level of SAPI services is useful for 
developed use speech recognition and TTS 
services. 
 
4. Application for reading information 
on Internet (searching by word) using 
web services or speech synthesis from 
text files, Word and Excel 
To accomplish such application the tech-
nologies used are: 
- Microsoft. NET Framework 2.0 package 
- MySQL 4.1 (in which is made database) 
- MyODBC 3.5.1 (for connection to 
MySQL) 
- Programming languages to access data-
base: C, C++, Java, PHP 
- Audio programs for recording, 
processing and editing wave 
- MBROLA synthesizer. 
The interface with user contains: 
• Levels of pre-proceeding text 
• Reading information from files 
• Accessing and reading information from 
web services. 
Pre-proceeding text requires: 
- connection to database by phonemes and 
waves 
- use phonemes dictionary of Romanian 
language (from MBROLA synthesizer)  
- pre-proceeding of the text which can 
contain letters and numbers; 
- conversion of the text in .pho format, 
which can be read by MBROLA; 
- conversion in wave format.  Revista Informatica Economică nr. 2(46)/2008 
 
139
Reading information from Word or Excel  
files requires adding COM references from 
working with them. File reading is made by 
writing its name and extension into Text Box 
Audio. 
In application’s interface was added the op-
tion to print the text in Braille format and 
print preview before printing, because learn-
ing by two channels, hearing and touching, 
assures to memorize the information for a 
long period of time. 
Conclusions 
For creating software products, the develop-
ers must take in account compatibility be-
tween their products and accessibility stan-
dards. 
The accessibility, for persons with disabili-
ties, means the use of the instruments which 
have on its basis the speech synthesis. 
Reproducing of a natural voice remains an 
open path for research and a challenge for 
software designers. 
 
References 
[1] Amundsen, M., MAPI, SAPI and  TAPI 
Developer’s Guide, SAMS, 1996; 
[2] Pollard, C, Sag, I.A. - Head-driven 
Phrase Structured Grammar, CSLI, 1994; 
[3]  Reveiu, A., Dârdală, M., Designing of 
accessible software for economic and social 
inclusion, The Proceedings of the 6th Bienni-
al International Symposium, SIMPEC 2006, 
Braşov; 
[4]  Smeureanu, I., Dârdală, M., Reveiu, A., 
VISUAL C# .NET, Editura CISON, 
Bucureşti, 2004; 
[5]  MBROLA: http://tcts.fpms.ac.be/ 
[6]   Ferency, A., Zaiu, D., Ferencz, M. , 
Raţiu, T.   Sistem Text-To-Speech pentru 
Limba Română; http://www.racai.ro/ 
[7]***, Accessibility in Microsoft Products 
http://www.microsoft.com/enable/ 

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