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java.lang.Objectedu.cmu.sphinx.frontend.frequencywarp.MelFilter
Defines a triangular mel-filter.
The MelFrequencyFilterBank
creates mel-filters and filters spectrum data using the method
filterOutput
.
A mel-filter is a triangular shaped bandpass filter. When a
mel-filter is constructed, the parameters leftEdge
,
rightEdge
, centerFreq
,
initialFreq
, and deltaFreq
are given to
the Constructor
. The first three arguments to the
constructor, i.e. leftEdge
, rightEdge
,
and centerFreq
, specify the filter's slopes. The total
area under the filter is 1. The filter is shaped as a
triangle. Knowing the distance between the center frequency and
each of the edges, it is easy to compute the slopes of the two
sides in the triangle - the third side being the frequency
axis. The last two arguments, initialFreq
and
deltaFreq
, identify the first frequency bin that falls
inside this filter and the spacing between successive frequency
bins. All frequencies here are considered in a linear scale.
Figure 1 below shows pictorially what the other parameters mean.
MelFrequencyFilterBank
Constructor Summary | |
MelFilter(double leftEdge,
double centerFreq,
double rightEdge,
double initialFreq,
double deltaFreq)
Constructs a filter from the parameters. |
Method Summary | |
double |
filterOutput(double[] spectrum)
Compute the output of a filter. |
Methods inherited from class java.lang.Object |
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
public MelFilter(double leftEdge, double centerFreq, double rightEdge, double initialFreq, double deltaFreq) throws java.lang.IllegalArgumentException
leftEdge
- the filter's lowest passing frequencycenterFreq
- the filter's center frequencyrightEdge
- the filter's highest passing frequencyinitialFreq
- the first frequency bin in the pass banddeltaFreq
- the step in the frequency axis between
frequency bins
java.lang.IllegalArgumentException
Method Detail |
public double filterOutput(double[] spectrum)
spectrum
- the input power spectrum to be filtered
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