Toward Sensor to Reproduce Human Sense - The Electronic Nose Artificial Olfaction Technology - page 113

Chapter 5
Toward Sensor to Reproduce Human
Sense
5.1 Introduction
We are constantly engaging in a chemical communication with environment. Our
bodies smell and by doing so we release relevant information about ourselves. Some
of this information is released in the form of volatiles and some is even detectable by
the human nose. Other signals are only perceivable by biological antennae. Bacteria
communicate using chemical signals, by releasing and receiving signaling mole-
cules in what is known as quorum sensing. They don't just communicate amongst
themselves but also interact with signals sent by their human host.
The human nose involved in the four functions of odor sensing: detection,
recording, memory search and recognition, which are replicated by machines, identify
as electronic noses (E-noses). This e-nose which contains chemical sensors, which is
used for detecting and recording; and in addition artificial intelligence (AI) software
artificial neural network (ANN) is used for memory search and identification [ 1 ].
Smells reach the olfactory sensory neurons by way of two pathways. The first
pathway is through nostrils. The second pathway is through a channel that con-
nects the roof of the throat region to the nose. When human chew food, aromas are
released that access the olfactory sensory neurons through this channel. If the
channel is blocked, such as when noses are stuffed up from a cold, odors cannot
reach the sensory cells and human ability to enjoy a food's flavor is lost. This is the
technique in which, senses of smell and taste work closely together. Without the
olfactory sensory neurons, familiar flavors like pineapple or strawberry would be
hard to differentiate. People who go to the doctor because they think they've lost
their sense of taste are surprised to learn that they have a smell disorder instead.
Our sense of smell is also influenced by something called the common chemical
sense. This sense involves thousands of nerve endings, especially on the moist
surfaces of the eyes, nose, mouth, and throat. These nerve endings help us sense
irritating substances such as the tear-inducing power of an onion or the refreshing
cool of peppermint.
Some of the fundamental signal-analysis techniques that find wide application
with bio-signals are discussed.