In the near future, speech recognition will become the method of
choice for controlling appliances, toys, tools, computers and robotics.
There is a huge commercial market waiting for this technology to mature.
This article details the construction and building of a stand
alone trainable speech recognition circuit that may be interfaced to
control just about anything electrical, such as; appliances, robots,
test instruments, VCR's TV's, etc. The circuit is trained (programmed)
to recognized words you want it to recognize.
To control and command an appliance (computer, VCR, TV security
system, etc.) by speaking to it, will make it easier, while increasing
the efficiency and effectiveness of working with that device.
At its most basic level speech recognition allows the user to
perform parallel tasks, (i.e. hands and eyes are busy elsewhere) while
continuing to work with the computer or appliance.
This circuit allows one to experiment with many facets of speech recognition technology.
The heart of the circuit is the HM2007 speech recognition
integrated circuit. The chip provides the options of recognizing either
forty .96 second words or twenty 1.92 second words. This circuit allows
the user to choose either the .96 second word length (40 word
vocabulary) or the 1.92 second word length (20 word vocabulary). For
memory the circuit uses an 8K X 8 static RAM.
The chip has two operational modes; manual mode and CPU mode.
The CPU mode is designed to allow the chip to work under a host
computer. This is an attractive approach to speech recognition for
computers because the speech recognition chip operates as a co-processor
to the main CPU. The jobs of listening and recognition doesn't
occupying any of the computer's CPU time. When the HM2007 recognizes a
command it can signal an interrupt to the host CPU and then relay the
command code. The HM2007 chip can be cascaded to provide a larger word
recognition library.
The SR-07 circuit we are building operates in the manual mode.
The manual mode allows one to build a stand alone speech recognition
board that doesn't require a host computer and may be integrated into
other devices to utilize speech control.
Applications
- Command and control of appliances and equipment
- Telephone assistance systems
- Data entry
- Speech controlled toys
- Speech and voice recognition security systems
Software Approach
Currently most speech recognition systems available today are
programs that use personal computers. The add on programs operate
continuously in the background of the computers operating system
(windows, OS/2, etc.). These programs require the computer to be
equipped with a compatible sound card. The disadvantage in this approach
is the necessity of a computer. While these speech programs are
impressive, it is not economically viable for manufacturers to add full
blown computer systems to control a washing machine or VCR. At best the
programs add to the processing required of the computer's CPU. There is a
noticeable slow down in the operation and function of the computer when
voice recognition is enabled.
Learning to Listen
We take our ability to listen for granted. For instance we are
capable of listening to one person speak among several at a party. We
sub-consciously filter out the extemporaneous conversations and sound.
This filtering ability is beyond the capabilities of today's speech
recognition systems.
Speech recognition is not speech understanding. Understanding
the meaning of words is a higher intellectual function. Because a
computer can respond to a vocal command does not mean it understands the
command spoken. Voice recognition system will one day have the ability
to distinguish linguistic nuances and meaning of words, to "Do what I
mean, not what I say!"