You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
168 lines
5.3 KiB
168 lines
5.3 KiB
<!DOCTYPE html>
|
|
|
|
<!--Converted with LaTeX2HTML 2002-2-1 (1.71)
|
|
original version by: Nikos Drakos, CBLU, University of Leeds
|
|
* revised and updated by: Marcus Hennecke, Ross Moore, Herb Swan
|
|
* with significant contributions from:
|
|
Jens Lippmann, Marek Rouchal, Martin Wilck and others -->
|
|
<HTML>
|
|
<HEAD>
|
|
|
|
<meta name="viewport" content="width=device-width, initial-scale=1.0">
|
|
|
|
|
|
<TITLE>Equalizing filters</TITLE>
|
|
<META NAME="description" CONTENT="Equalizing filters">
|
|
<META NAME="keywords" CONTENT="book">
|
|
<META NAME="resource-type" CONTENT="document">
|
|
<META NAME="distribution" CONTENT="global">
|
|
|
|
<META NAME="Generator" CONTENT="LaTeX2HTML v2002-2-1">
|
|
<META HTTP-EQUIV="Content-Style-Type" CONTENT="text/css">
|
|
|
|
<LINK REL="STYLESHEET" HREF="book.css">
|
|
|
|
<LINK REL="previous" HREF="node130.html">
|
|
<LINK REL="up" HREF="node128.html">
|
|
<LINK REL="next" HREF="node132.html">
|
|
</HEAD>
|
|
|
|
<BODY >
|
|
<!--Navigation Panel-->
|
|
<A ID="tex2html2533"
|
|
HREF="node132.html">
|
|
<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next"
|
|
SRC="next.png"></A>
|
|
<A ID="tex2html2527"
|
|
HREF="node128.html">
|
|
<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up"
|
|
SRC="up.png"></A>
|
|
<A ID="tex2html2523"
|
|
HREF="node130.html">
|
|
<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous"
|
|
SRC="prev.png"></A>
|
|
<A ID="tex2html2529"
|
|
HREF="node4.html">
|
|
<IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents"
|
|
SRC="contents.png"></A>
|
|
<A ID="tex2html2531"
|
|
HREF="node201.html">
|
|
<IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index"
|
|
SRC="index.png"></A>
|
|
<BR>
|
|
<B> Next:</B> <A ID="tex2html2534"
|
|
HREF="node132.html">Elementary filters</A>
|
|
<B> Up:</B> <A ID="tex2html2528"
|
|
HREF="node128.html">Taxonomy of filters</A>
|
|
<B> Previous:</B> <A ID="tex2html2524"
|
|
HREF="node130.html">Band-pass and stop-band filters</A>
|
|
<B> <A ID="tex2html2530"
|
|
HREF="node4.html">Contents</A></B>
|
|
<B> <A ID="tex2html2532"
|
|
HREF="node201.html">Index</A></B>
|
|
<BR>
|
|
<BR>
|
|
<!--End of Navigation Panel-->
|
|
|
|
<H2><A ID="SECTION001213000000000000000"></A>
|
|
<A ID="sect8.equalizing"></A>
|
|
<BR>
|
|
Equalizing filters
|
|
</H2>
|
|
|
|
<P>
|
|
In some applications, such as
|
|
<A ID="10107"></A><I>equalization</I>,
|
|
the goal isn't to pass signals of certain frequencies while stopping others
|
|
altogether, but to make controllable adjustments, boosting or attenuating
|
|
a signal, over a frequency range, by a desired gain. Two filter types
|
|
are useful for this. First, a
|
|
<A ID="10109"></A><A ID="10110"></A><I>shelving filter</I>
|
|
(Figure <A HREF="#fig08.05">8.5</A>) is used for selectively boosting or reducing either the
|
|
low or high end of the frequency range. Below a selectable crossover frequency,
|
|
the filter tends toward a low-frequency gain, and above it it tends toward a
|
|
different, high-frequency one. The crossover frequency, low-frequency gain,
|
|
and high-frequency gain can all be adjusted independently.
|
|
|
|
<P>
|
|
|
|
<DIV ALIGN="CENTER"><A ID="fig08.05"></A><A ID="10115"></A>
|
|
<TABLE>
|
|
<CAPTION ALIGN="BOTTOM"><STRONG>Figure 8.5:</STRONG>
|
|
A shelving filter, showing low and high frequency gain, and
|
|
crossover frequency.</CAPTION>
|
|
<TR><TD><IMG
|
|
WIDTH="312" HEIGHT="211" BORDER="0"
|
|
SRC="img858.png"
|
|
ALT="\begin{figure}\psfig{file=figs/fig08.05.ps}\end{figure}"></TD></TR>
|
|
</TABLE>
|
|
</DIV>
|
|
|
|
<P>
|
|
Second, a
|
|
<A ID="10118"></A><A ID="10119"></A><I>peaking filter</I>
|
|
(Figure <A HREF="#fig08.06">8.6</A>) is capable of boosting or attenuating signals within
|
|
a range of frequencies. The center frequency and bandwidth (which together
|
|
control the range of frequencies affected), and the in-band and out-of-band
|
|
gains are separately adjustible.
|
|
|
|
<P>
|
|
|
|
<DIV ALIGN="CENTER"><A ID="fig08.06"></A><A ID="10124"></A>
|
|
<TABLE>
|
|
<CAPTION ALIGN="BOTTOM"><STRONG>Figure 8.6:</STRONG>
|
|
A peaking filter, with controllable center frequency, bandwidth,
|
|
and in-band and out-of-band gains.</CAPTION>
|
|
<TR><TD><IMG
|
|
WIDTH="290" HEIGHT="243" BORDER="0"
|
|
SRC="img859.png"
|
|
ALT="\begin{figure}\psfig{file=figs/fig08.06.ps}\end{figure}"></TD></TR>
|
|
</TABLE>
|
|
</DIV>
|
|
|
|
<P>
|
|
Parametric equalizers often employ two shelving filters (one each to adjust
|
|
the low and high ends of the spectrum) and two or three peaking filters to
|
|
adjust bands in between.
|
|
|
|
<P>
|
|
<HR>
|
|
<!--Navigation Panel-->
|
|
<A ID="tex2html2533"
|
|
HREF="node132.html">
|
|
<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next"
|
|
SRC="next.png"></A>
|
|
<A ID="tex2html2527"
|
|
HREF="node128.html">
|
|
<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up"
|
|
SRC="up.png"></A>
|
|
<A ID="tex2html2523"
|
|
HREF="node130.html">
|
|
<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous"
|
|
SRC="prev.png"></A>
|
|
<A ID="tex2html2529"
|
|
HREF="node4.html">
|
|
<IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents"
|
|
SRC="contents.png"></A>
|
|
<A ID="tex2html2531"
|
|
HREF="node201.html">
|
|
<IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index"
|
|
SRC="index.png"></A>
|
|
<BR>
|
|
<B> Next:</B> <A ID="tex2html2534"
|
|
HREF="node132.html">Elementary filters</A>
|
|
<B> Up:</B> <A ID="tex2html2528"
|
|
HREF="node128.html">Taxonomy of filters</A>
|
|
<B> Previous:</B> <A ID="tex2html2524"
|
|
HREF="node130.html">Band-pass and stop-band filters</A>
|
|
<B> <A ID="tex2html2530"
|
|
HREF="node4.html">Contents</A></B>
|
|
<B> <A ID="tex2html2532"
|
|
HREF="node201.html">Index</A></B>
|
|
<!--End of Navigation Panel-->
|
|
<ADDRESS>
|
|
Miller Puckette
|
|
2006-12-30
|
|
</ADDRESS>
|
|
</BODY>
|
|
</HTML>
|
|
|