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.
181 lines
5.8 KiB
181 lines
5.8 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>Reverberator</TITLE>
|
|
<META NAME="description" CONTENT="Reverberator">
|
|
<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="next" HREF="node125.html">
|
|
<LINK REL="previous" HREF="node123.html">
|
|
<LINK REL="up" HREF="node116.html">
|
|
<LINK REL="next" HREF="node125.html">
|
|
</HEAD>
|
|
|
|
<BODY >
|
|
<!--Navigation Panel-->
|
|
<A ID="tex2html2403"
|
|
HREF="node125.html">
|
|
<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next"
|
|
SRC="next.png"></A>
|
|
<A ID="tex2html2397"
|
|
HREF="node116.html">
|
|
<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up"
|
|
SRC="up.png"></A>
|
|
<A ID="tex2html2391"
|
|
HREF="node123.html">
|
|
<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous"
|
|
SRC="prev.png"></A>
|
|
<A ID="tex2html2399"
|
|
HREF="node4.html">
|
|
<IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents"
|
|
SRC="contents.png"></A>
|
|
<A ID="tex2html2401"
|
|
HREF="node201.html">
|
|
<IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index"
|
|
SRC="index.png"></A>
|
|
<BR>
|
|
<B> Next:</B> <A ID="tex2html2404"
|
|
HREF="node125.html">Pitch shifter</A>
|
|
<B> Up:</B> <A ID="tex2html2398"
|
|
HREF="node116.html">Examples</A>
|
|
<B> Previous:</B> <A ID="tex2html2392"
|
|
HREF="node123.html">Time-varying complex comb filter:</A>
|
|
<B> <A ID="tex2html2400"
|
|
HREF="node4.html">Contents</A></B>
|
|
<B> <A ID="tex2html2402"
|
|
HREF="node201.html">Index</A></B>
|
|
<BR>
|
|
<BR>
|
|
<!--End of Navigation Panel-->
|
|
|
|
<H2><A ID="SECTION0011108000000000000000">
|
|
Reverberator</A>
|
|
</H2>
|
|
|
|
<P>
|
|
Example G08.reverb.pd (Figure <A HREF="#fig07.31">7.31</A>) shows a simple artificial reverberator,
|
|
essentially a realization of the design shown in Figure <A HREF="node111.html#fig07.15">7.15</A>. Four
|
|
delay lines are fed by the input and by their own recirculated output. The
|
|
delay outputs are intermixed using rotation matrices, built up from elementary
|
|
rotations of <IMG
|
|
WIDTH="29" HEIGHT="32" ALIGN="MIDDLE" BORDER="0"
|
|
SRC="img52.png"
|
|
ALT="$\pi /4$"> as in Figure <A HREF="node110.html#fig07.13">7.13</A> (part a).
|
|
|
|
<P>
|
|
|
|
<DIV ALIGN="CENTER"><A ID="fig07.31"></A><A ID="8301"></A>
|
|
<TABLE>
|
|
<CAPTION ALIGN="BOTTOM"><STRONG>Figure 7.31:</STRONG>
|
|
An artificial reverberator.</CAPTION>
|
|
<TR><TD><IMG
|
|
WIDTH="585" HEIGHT="811" BORDER="0"
|
|
SRC="img846.png"
|
|
ALT="\begin{figure}\psfig{file=figs/fig07.31.ps}\end{figure}"></TD></TR>
|
|
</TABLE>
|
|
</DIV>
|
|
|
|
<P>
|
|
The normalizing
|
|
multiplication (by <IMG
|
|
WIDTH="43" HEIGHT="38" ALIGN="MIDDLE" BORDER="0"
|
|
SRC="img847.png"
|
|
ALT="$\sqrt{1/2}$"> at each stage) is absorbed into the feedback
|
|
gain, which therefore cannot exceed <IMG
|
|
WIDTH="27" HEIGHT="32" ALIGN="MIDDLE" BORDER="0"
|
|
SRC="img98.png"
|
|
ALT="$1/2$">.
|
|
At a feedback gain of exactly <IMG
|
|
WIDTH="27" HEIGHT="32" ALIGN="MIDDLE" BORDER="0"
|
|
SRC="img98.png"
|
|
ALT="$1/2$">, all the energy leaving the delay lines is
|
|
reinserted into them, so the reverberation lasts perpetually.
|
|
|
|
<P>
|
|
|
|
<DIV ALIGN="CENTER"><A ID="fig07.32"></A><A ID="8307"></A>
|
|
<TABLE>
|
|
<CAPTION ALIGN="BOTTOM"><STRONG>Figure 7.32:</STRONG>
|
|
The echo generator used in the reverberator.</CAPTION>
|
|
<TR><TD><IMG
|
|
WIDTH="230" HEIGHT="164" BORDER="0"
|
|
SRC="img848.png"
|
|
ALT="\begin{figure}\psfig{file=figs/fig07.32.ps}\end{figure}"></TD></TR>
|
|
</TABLE>
|
|
</DIV>
|
|
|
|
<P>
|
|
Figure <A HREF="#fig07.32">7.32</A> shows the interior of the <TT>reverb-echo</TT> abstraction
|
|
used in the reverberator. The two inputs are mixed (using the same rotation matrix
|
|
and again leaving the renormalization for later). One channel is then
|
|
delayed. The delay times are selected to grow roughly exponentially; this
|
|
ensures a smooth and spread-out pattern of echos.
|
|
|
|
<P>
|
|
Many extensions of this idea are possible of which we'll only name a few. It
|
|
is natural, first, to put low-pass filters at the end of the delay lines, to
|
|
mimic the typically faster decay of high frequencies than low ones. It is also
|
|
common to use more than four recirculating delays; one reverberator in the Pd
|
|
distribution uses sixteen. Finally, it is common to allow separate control of
|
|
the amplitudes of the early echos (heard directly) and that of the
|
|
recirculating signal; parameters such as these are thought to control
|
|
sonic qualities described as "presence", "warmth", "clarity", and so on.
|
|
|
|
<P>
|
|
<HR>
|
|
<!--Navigation Panel-->
|
|
<A ID="tex2html2403"
|
|
HREF="node125.html">
|
|
<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next"
|
|
SRC="next.png"></A>
|
|
<A ID="tex2html2397"
|
|
HREF="node116.html">
|
|
<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up"
|
|
SRC="up.png"></A>
|
|
<A ID="tex2html2391"
|
|
HREF="node123.html">
|
|
<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous"
|
|
SRC="prev.png"></A>
|
|
<A ID="tex2html2399"
|
|
HREF="node4.html">
|
|
<IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents"
|
|
SRC="contents.png"></A>
|
|
<A ID="tex2html2401"
|
|
HREF="node201.html">
|
|
<IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index"
|
|
SRC="index.png"></A>
|
|
<BR>
|
|
<B> Next:</B> <A ID="tex2html2404"
|
|
HREF="node125.html">Pitch shifter</A>
|
|
<B> Up:</B> <A ID="tex2html2398"
|
|
HREF="node116.html">Examples</A>
|
|
<B> Previous:</B> <A ID="tex2html2392"
|
|
HREF="node123.html">Time-varying complex comb filter:</A>
|
|
<B> <A ID="tex2html2400"
|
|
HREF="node4.html">Contents</A></B>
|
|
<B> <A ID="tex2html2402"
|
|
HREF="node201.html">Index</A></B>
|
|
<!--End of Navigation Panel-->
|
|
<ADDRESS>
|
|
Miller Puckette
|
|
2006-12-30
|
|
</ADDRESS>
|
|
</BODY>
|
|
</HTML>
|
|
|