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<document xmlns="http://cnx.rice.edu/cnxml" xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/" id="Module.2003-12-16.4123">
  <name>The Problems with Distortion</name>
  <metadata>
  <md:version>1.2</md:version>
  <md:created>2003/12/16 14:41:23 US/Central</md:created>
  <md:revised>2003/12/17 16:00:57.038 US/Central</md:revised>
  <md:authorlist>
    <md:author id="lizzardg">
      <md:firstname>Elizabeth</md:firstname>
      
      <md:surname>Gregory</md:surname>
      <md:email>lizzardg@rice.edu</md:email>
    </md:author>
    <md:author id="jbuck">
      <md:firstname>Jason</md:firstname>
      <md:othername>A</md:othername>
      <md:surname>Buck</md:surname>
      <md:email>jbuck@rice.edu</md:email>
    </md:author>
  </md:authorlist>

  <md:maintainerlist>
    <md:maintainer id="lizzardg">
      <md:firstname>Elizabeth</md:firstname>
      
      <md:surname>Gregory</md:surname>
      <md:email>lizzardg@rice.edu</md:email>
    </md:maintainer>
    <md:maintainer id="mhusband">
      <md:firstname>Mark</md:firstname>
      <md:othername>S.</md:othername>
      <md:surname>Husband</md:surname>
      <md:email>mhusband@rice.edu</md:email>
    </md:maintainer>
    <md:maintainer id="richb">
      <md:firstname>Richard</md:firstname>
      <md:othername>G.</md:othername>
      <md:surname>Baraniuk</md:surname>
      <md:email>richb@rice.edu</md:email>
    </md:maintainer>
    <md:maintainer id="jbuck">
      <md:firstname>Jason</md:firstname>
      <md:othername>A</md:othername>
      <md:surname>Buck</md:surname>
      <md:email>jbuck@rice.edu</md:email>
    </md:maintainer>
  </md:maintainerlist>
  
  <md:keywordlist>
    <md:keyword>distortion</md:keyword>
    <md:keyword>nonlinear</md:keyword>
    <md:keyword>harmonics</md:keyword>
    <md:keyword>Taylor Series</md:keyword>
  </md:keywordlist>

  <md:abstract>In trying to model distortion, a few noise problems and seemingly failed method arise.</md:abstract>
</metadata>

  <content>
    <para id="p1">
      Let's say you go out to Radio Shack and buy a few cheap cables
      that let you plug in your slammin' new guitar into your
      soundcard, just so you can play around with different
      distortions.  You want try playing with MATLAB, using the Taylor
      Series method's familiar discrete power series:
      <equation id="p1e1">
	<m:math>
	  <m:apply>
	    <m:eq/>
	    <m:ci>y</m:ci>
	    <m:apply>
	      <m:sum/>
	      <m:bvar>
		<m:ci>n</m:ci>
	      </m:bvar>
	      <m:lowlimit>
		<m:cn>0</m:cn>
	      </m:lowlimit>
	      <m:uplimit>
		<m:ci>N</m:ci>
	      </m:uplimit>
	      <m:apply>
		<m:times/>
		<m:ci><m:msub>
		    <m:mi>a</m:mi>
		    <m:mi>n</m:mi>
		  </m:msub></m:ci>
		<m:apply>
		  <m:power/>
		  <m:ci>x</m:ci>
		  <m:ci>n</m:ci>
		</m:apply>
	      </m:apply>
	    </m:apply>
	  </m:apply>
	</m:math>
      </equation>
      where <m:math><m:ci>x</m:ci></m:math> is your original signal,
      <m:math><m:ci>y</m:ci></m:math> is your distorted signal, and 
      <m:math>
	<m:ci><m:msub> 
	    <m:mi>a</m:mi> 
	    <m:mi>n</m:mi> 
	  </m:msub></m:ci>
      </m:math> is the constant for each item of the sum.
    </para>
    <para id="p2">
      The first problem you notice in playing back your
      <code>wav</code> file is the noise; after all, those were some
      really cheap cables!  However, from an introductory electrical
      engineering class and another signals class, you've learned how
      to filter out noise, so that should be easy to deal with later.
    </para>
    <para id="p3">
      You notice the next problem when trying to execute the Taylor
      Series approximation of the signals.  You may set some
      harmonics' constants to zero, but as you increase different
      coefficients of higher and higher powers, the only difference is
      that the music has a lower volume, and the volume of the noise
      is higher!  Why isn't this working?
    </para>   
  </content>
  
</document>
