Information Technology Reference
In-Depth Information
In Eqs. 7 and 8, it has been used, respectively, the mean and variance statistical
operators
M
(9)
1
ˆ
[]
∑
=
E
Y
≡
μ
≡
y
m
M
m
1
M
1
[]
(
)
(10)
2
∑
=
2
Var
Y
≡
σ
ˆ
≡
y
−
μ
m
M
m
1
where
M
represents the number of values of a given random variable
Y
.
Note that the previously described statistical characterization can be done for all
the available features
f
∈
Γ
so that the feature extraction algorithm generates
k
(11)
[
ˆ
[] []
[
]
ˆ
[
]
[
[
]
]
]
2
2
F
=
E
F
,
σ
ˆ
F
,
"
,
E
F
,
σ
ˆ
F
1
1
N
N
F
F
a random vector whose dimension is
dim
(
F
) = 2
N
F
=
m
.
This is just the signal-describing vector that should feed the classifier. For the sake
of clarity, it is written as
[
]
F
.
Finally, taking this data structure in mind, the immediate goal is:
Given the set of
N
F
available, general-purpose features,
=
F
1
"
,
,
F
F
(12)
{
}
Γ
=
f
1
"
,
,
f
N
F
to select a subset
Φ
⊆
Γ
that minimizes the mean error probability of correct
classification.
Finding the solution requires, for any candidate feature subset
Φ
⊆
Γ
, the follow-
ing sequence of operations:
•
Feeding the complete system with input audio files from a proper database,
which will be described in Section 5.1
•
Calculating the feature vector for the complete file, as previously explained
•
Classifying, and
•
Calculating the mean squared error (MSE) between the classifier output and
the correct output, and the probability of correct classification.
As shown, the process of selecting a subset containing those more appropriate fea-
tures, those that minimize the classification error probability, is very complex. The
feasibly of the HS method is now explored.
4 Harmony Search Algorithm in a Nutshell
Harmony search (HS) algorithm is a meta-heuristic searching procedure inspired by
the processes of music creation and improvisation. In these activities, musicians look
for the 'best' combination of sounds in order to produce esthetically pleasant compo-
sitions [16-21]. In such improvisation process of composition, the musician remem-
bers those pieces of music that sound melodiously and that can be used in order to
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