replace '<A NAME=' with '<A ID='
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node78.html
68
node78.html
@@ -30,50 +30,50 @@ original version by: Nikos Drakos, CBLU, University of Leeds
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<BODY >
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<!--Navigation Panel-->
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<A NAME="tex2html1711"
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<A ID="tex2html1711"
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HREF="node79.html">
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<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next"
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SRC="next.png"></A>
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<A NAME="tex2html1705"
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<A ID="tex2html1705"
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HREF="node75.html">
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<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up"
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SRC="up.png"></A>
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<A ID="tex2html1699"
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HREF="node77.html">
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SRC="prev.png"></A>
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<A NAME="tex2html1707"
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<A ID="tex2html1707"
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HREF="node4.html">
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<IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents"
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SRC="contents.png"></A>
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<A NAME="tex2html1709"
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<A ID="tex2html1709"
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HREF="node201.html">
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<IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index"
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SRC="index.png"></A>
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<BR>
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<B> Next:</B> <A NAME="tex2html1712"
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<B> Next:</B> <A ID="tex2html1712"
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HREF="node79.html">Frequency and phase modulation</A>
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<B> Up:</B> <A NAME="tex2html1706"
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<B> Up:</B> <A ID="tex2html1706"
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HREF="node75.html">Modulation</A>
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<B> Previous:</B> <A NAME="tex2html1700"
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<B> Previous:</B> <A ID="tex2html1700"
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HREF="node77.html">Multiplying audio signals</A>
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<B> <A NAME="tex2html1708"
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<B> <A ID="tex2html1708"
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HREF="node4.html">Contents</A></B>
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<B> <A NAME="tex2html1710"
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<B> <A ID="tex2html1710"
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HREF="node201.html">Index</A></B>
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<BR>
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<BR>
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<!--End of Navigation Panel-->
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<H1><A NAME="SECTION00930000000000000000"></A>
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<A NAME="sect5.waveshaping"></A>
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<H1><A ID="SECTION00930000000000000000"></A>
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<A ID="sect5.waveshaping"></A>
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<BR>
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Waveshaping
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</H1>
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<P>
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Another approach to modulating a signal, called
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<A NAME="5674"></A><I>waveshaping</I>,
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<A ID="5674"></A><I>waveshaping</I>,
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is simply to pass it through a
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suitably chosen nonlinear function. A block diagram for doing this is shown in Figure
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<A HREF="#fig05.05">5.5</A>.
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@@ -81,7 +81,7 @@ The function <IMG
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WIDTH="25" HEIGHT="32" ALIGN="MIDDLE" BORDER="0"
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SRC="img14.png"
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ALT="$f()$"> (called the
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<A NAME="5677"></A><I>transfer function</I>)
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<A ID="5677"></A><I>transfer function</I>)
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distorts the incoming waveform into a different shape. The new shape depends
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on the shape of the incoming wave, on the transfer function, and
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also--crucially--on
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@@ -94,7 +94,7 @@ operation, as shown in the block diagram.
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<P>
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<DIV ALIGN="CENTER"><A NAME="fig05.05"></A><A NAME="5681"></A>
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<DIV ALIGN="CENTER"><A ID="fig05.05"></A><A ID="5681"></A>
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<TABLE>
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<CAPTION ALIGN="BOTTOM"><STRONG>Figure 5.5:</STRONG>
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Block diagram for waveshaping an input signal using a nonlinear
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@@ -113,7 +113,7 @@ the different effect of the wavetable lookup at different amplitudes.</CAPTION>
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<P>
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The amplitude of the incoming waveform is called the waveshaping
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<A NAME="5684"></A><I>index</I>. In many situations a small index leads to relatively little
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<A ID="5684"></A><I>index</I>. In many situations a small index leads to relatively little
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distortion (so that the output closely resembles the input) and a larger one
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gives a more distorted, richer timbre.
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@@ -123,7 +123,7 @@ Figure <A HREF="#fig05.06">5.6</A> shows a familiar example of waveshaping, in w
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WIDTH="25" HEIGHT="32" ALIGN="MIDDLE" BORDER="0"
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SRC="img14.png"
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ALT="$f()$"> amounts to a
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<A NAME="5687"></A>
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<A ID="5687"></A>
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<I>clipping function</I>. This example shows clearly how the input
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amplitude--the index--can
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affect the output waveform. The clipping function passes its input
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@@ -138,12 +138,12 @@ at the end. This effect will be well known to anyone who has played an
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instrument through an overdriven amplifier. The louder the input, the
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more distorted will be the output. For this reason, waveshaping is also sometimes
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called
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<A NAME="5689"></A>
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<A ID="5689"></A>
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<I>distortion</I>.
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<P>
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<DIV ALIGN="CENTER"><A NAME="fig05.06"></A><A NAME="5693"></A>
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<DIV ALIGN="CENTER"><A ID="fig05.06"></A><A ID="5693"></A>
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<TABLE>
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<CAPTION ALIGN="BOTTOM"><STRONG>Figure 5.6:</STRONG>
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Clipping as an example of waveshaping: (a) the input, a decaying
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@@ -225,7 +225,7 @@ of the input.
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<P>
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<DIV ALIGN="CENTER"><A NAME="fig05.07"></A><A NAME="5942"></A>
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<DIV ALIGN="CENTER"><A ID="fig05.07"></A><A ID="5942"></A>
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<TABLE>
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<CAPTION ALIGN="BOTTOM"><STRONG>Figure 5.7:</STRONG>
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Waveshaping using a quadratic transfer function <IMG
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@@ -356,7 +356,7 @@ f(x+y) = {x^2} + 2 x y + {y^2}
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<BR CLEAR="ALL">
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<P></P>
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This effect, called
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<A NAME="5708"></A><I>intermodulation</I>,
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<A ID="5708"></A><I>intermodulation</I>,
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becomes more and more dominant as the number of terms in the input
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increases; if there are <IMG
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WIDTH="12" HEIGHT="14" ALIGN="BOTTOM" BORDER="0"
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@@ -531,7 +531,7 @@ an incoming signal, it is sometimes useful to write the function <IMG
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SRC="img112.png"
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ALT="$f$"> as
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a finite or infinite
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<A NAME="5712"></A><I>power series</I>:
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<A ID="5712"></A><I>power series</I>:
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<BR><P></P>
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<DIV ALIGN="CENTER">
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<!-- MATH
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@@ -705,8 +705,8 @@ x[n] = \cos (\omega n)
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<BR CLEAR="ALL">
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<P></P>
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and so on.
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<A NAME="eq-waveshaping"></A>The numerators of the fractions will be recognized as Pascal's triangle. The
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<A NAME="5747"></A>Central Limit Theorem
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<A ID="eq-waveshaping"></A>The numerators of the fractions will be recognized as Pascal's triangle. The
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<A ID="5747"></A>Central Limit Theorem
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of probability implies that each <IMG
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WIDTH="12" HEIGHT="14" ALIGN="BOTTOM" BORDER="0"
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SRC="img58.png"
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@@ -835,36 +835,36 @@ are developed in detail in Chapter <A HREF="node89.html#chapter-paf">6</A>.
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<P>
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SRC="up.png"></A>
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SRC="prev.png"></A>
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<A ID="tex2html1707"
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HREF="node4.html">
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<IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents"
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SRC="contents.png"></A>
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<A NAME="tex2html1709"
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<A ID="tex2html1709"
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HREF="node201.html">
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<IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index"
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SRC="index.png"></A>
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<BR>
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<B> Next:</B> <A NAME="tex2html1712"
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<B> Next:</B> <A ID="tex2html1712"
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HREF="node79.html">Frequency and phase modulation</A>
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<B> Up:</B> <A NAME="tex2html1706"
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<B> Up:</B> <A ID="tex2html1706"
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HREF="node75.html">Modulation</A>
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<B> Previous:</B> <A NAME="tex2html1700"
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<B> Previous:</B> <A ID="tex2html1700"
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HREF="node77.html">Multiplying audio signals</A>
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<B> <A NAME="tex2html1708"
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<B> <A ID="tex2html1708"
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HREF="node4.html">Contents</A></B>
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<B> <A NAME="tex2html1710"
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<B> <A ID="tex2html1710"
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HREF="node201.html">Index</A></B>
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<!--End of Navigation Panel-->
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<ADDRESS>
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