Proposal—Voice Activated Control System

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17 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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Voice Activated Control System



Voice Activated Control System (VACS) by Mark Heuer

Transmitting, receiving, and processing speech is one of the largest, if not the
largest, area of communication technology. Because my
emphasis is in this field of
electrical engineering, I felt I could gain an edge and much needed experience by doing a
project on speech recognition. This project will give further understanding of related
areas, such as speech synthesis, speaker recognit
ion, and large vocabulary speech
recognition (for word processing). Thus, I find the project very interesting, applicable,
and practical.


The VACS will recognize simple spoken commands, such as “lights on,” and
respond accordingly; that is, i
t will send a wireless signal to a module connected to the
“lights,” telling the module to turn them “on.”

This same scenerio can be used for many other household systems

electric door
locks, CD changers, ceiling fans

anything that has a switch or is remot
e controlled.
Even old televisions that do not have a remote control

The power, volume, and channel
buttons can be “tapped” into and hooked up to remote modules. Individual lights can be
“named” and assigned a module. All additional modules can be contr
olled by one central
speech recognition unit.

Customer benefits:

Ends hassle of finding a light switch in the dark, just say the light’s name

Complete control over separate lights or appliances

Control words can be easy to remember appliance names or locat
ion of lights

Control words are completely reprogrammable

Add more modules to the existing control unit, anytime

Want to make sure you turned off the stove? Call from New Zealand and leave a
message on your answering machine: “stove…off.”

Product features

Stand alone system

Entire system consists of control unit and multiple modules,
no PC connection necessary

Portable control unit

Place in any room for best sound reception

Different modules can be used for different applications

Control a 220V outlet
a 5V power switch

Continuous time signal analysis

Sensitive receiver “hears” command from far away


Block Diagram:












Block Description:

Input Signal

This incoming audible signa
l includes both speech and noise. It
will be processed continually as the digital signal processor searches for a recognizable
command word.


The microphone will receive the sound waves and convert them to
a continuous (analog) variable voltage

signal. The microphone’s sensitivity will
determine how far away the person can be to send a successful command.


Only frequencies between 300 Hz and 3 kHz (typical vocal range) will
pass through the filter, eliminating most noise. The filtered a
nalog signal will then be
sent to the analog to digital converter.

A/D Converter

Here, the analog signal is converted into a digital pulse code
modulated (PCM) signal. Since a single command word must be recognized amid
background noise and similar
ing words, the digital encoding must be precise. A
typical sampling rate used for vocal
PCM signals is 8000 samples/sec (above the Nyquist
rate of 6000 samples/sec). Twelve bits/sample is sufficient for linear quantization. Thus,
the A/D converter must
output 12 kB/sec, continually.


While the system is running, this digital signal must be
searched, in continuous time, for a recognizable command. This is the job of the
microprocessor. The microprocessor will break the signal down into di
screte time
segments and compare them with the stored values in memory. If a match is found, the
microprocessor will send a signal to the transmitter, telling it, in turn, to transmit a
specific data sequence to the modules. The microprocessor will also
allow the control
words to be stored in memory.

Wireless Transmitter

The transmitter outputs an eight bit signal to the modules,
specifying the module corresponding to the control word, and how the module should
respond. The transmitter must have long ra
nge, sending the signal throughout the house,
yet transmit the data at a frequency that will not cause interference with radio, television,
or phone signals.

Remote module

“On” and “off” of the appliance is directly controlled by the
module. Every module

will receive the signal sent from the transmitter, but only one
module will respond to the signal, turning its appliance ‘on’ or ‘off.’


The memory is used for storage of the control words. The
microprocessor will control reading and writing from/
to the memory.

Digital Signal Processor

The DSP board already has the filter, A/D converter,
microprocessor, memory, and transmitter built in. The board will need to be programmed
to utilize all of these components in the correct manner.

Performance Requ

Each of the components listed above greatly affect the overall quality of the
VACS. The main feature affecting performance will be the DSP’s capability to filter out
noise from the desired signal. With a sensitive microphone, any noise within t
he house
will be received also, making it much harder for the DSP to decipher the command word.
However, the faster the DSP’s processing capabilities, the better the chance of the
incoming digital stream to be recognized, since the processor can be progra
mmed to
section, average, and process the stream with greater accuracy.


Testing procedures:

Much of the research and analysis for voice recognition will be done using
Matlab, since it offers a visual representation of audio signals, whi
le the DSP does not.
Once the best method for recognizing a command word is found, the DSP will be
programmed to perform that method. Numerous methods currently exist for processing
speech, utilizing different ways of sectioning, averaging, and comparing

the digital
stream. Matlab, with its ability to plot and compare sound waves, will be the fastest and
easiest way to experiment with these methods.

Since the main components are already contained on the DSP board, a large part
of this project will be pr
ogramming and debugging the code.

Other hardware research will be done on the transmitter/receiver pair. It will be
necessary to find the range and reliability of the signal. This can be done using simple
methods. For instance, send a continuous signal

from the transmitter telling the receiver
to turn a light on and off repeatedly. Then, walk the receiver and light away from the
transmitter. Where the signal is becomes too weak to read all the time, the light will
blink slower, or stop blinking. This

is the true range of the receiver/transmitter pair.

Tolerance Analysis:

Obviously, a key part of the entire system is comparing the incoming data stream
with the stored control words in memory. The problem is that when a control word
(“lights”) is utter
ed, converted, and filtered, it will not have the exact same digital
representation as the control word in memory. Therefore, a certain tolerance must be
allowed for matching words. But, if too much tolerance is allowed, words that sound
similar to the c
ontrol word (“life” compared to “light”) will also activate the system. The
research done on Matlab will conclude how much tolerance can be allowed.


Cost Analysis:

Labor: $50/hour * 2.5 * 15 hours/week * 10 weeks = $18750


DSP Board


Receiver Modules (2)

$10 each

Module/Light Link (2)

$10 each

Total Parts


Total Cost: Labor + Parts = $19140


Week of 2/5: Continue research on various speech recognition methods, find and

order suitable DSP, prop
osal due

Week of 2/12: Learn Matlab signal processing tools, learn DSP assembly

language, become familiar with DSP specs

Week of 2/19: Research signals of typical command words on Matlab, continue

learning DSP assembly language, programming, order tr
pair, design review

Week of 2/26: Research and test methods for processing continuous time audio

signals with Matlab

Week of 3/5: Programming

Week of 3/12: Spring Break

Week of 3/19: Programming

Week of 3/26: Debugging, mock


Week of 4/2: Debugging

Week of 4/9: Testing

Week of 4/16: Write final paper and prepare demo and presentation

Week of 4/23: Demo and presentation

Week of 4/30: Final papers and lab notebooks due