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169 lines
5.1 KiB
169 lines
5.1 KiB
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HREF="node26.html">Wavetables and samplers</A>
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HREF="node38.html">Automatic read point precession</A>
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<!--End of Navigation Panel-->
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<H1><A NAME="SECTION00670000000000000000">
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Exercises</A>
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</H1>
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<P>
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<OL>
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<LI>If a wavetable with <IMG
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WIDTH="35" HEIGHT="13" ALIGN="BOTTOM" BORDER="0"
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SRC="img296.png"
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ALT="$1000$"> samples is played back at unit transposition,
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at a sample rate of 44100 Hertz, how long does the resulting sound last?
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<P>
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</LI>
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<LI>A one-second wavetable is played back in 0.5 seconds. By what
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interval is the sound transposed?
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<P>
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</LI>
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<LI>Still assuming a one-second wavetable, if we play it back periodically
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(in a loop), at how many Hertz should we loop the wavetable to transpose the
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original sound upward one half-step?
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<P>
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</LI>
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<LI>We wish to play a wavetable (recorded at <IMG
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WIDTH="76" HEIGHT="14" ALIGN="BOTTOM" BORDER="0"
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SRC="img297.png"
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ALT="$R=44100$">), looping ten times
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per second, so that the original sound stored in the wavetable is transposed up
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a perfect fifth (see Page <A HREF="node14.html#r-intervals"><IMG ALIGN="BOTTOM" BORDER="1" ALT="[*]"
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SRC="crossref.png"></A>). How large a segment of the
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wavetable, in samples, should be played back?
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<P>
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</LI>
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<LI>Suppose you wish to use waveform stretching on a wavetable that holds a
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periodic waveform of period 100. You wish to hear the untransposed spectrum at
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a period of 200 samples. By what duty factor should you squeeze the waveform?
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<P>
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</LI>
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<LI>The first half of a wavetable contains a cycle of a sinusoid of peak
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amplitude one. The second half contains zeros. What is the strength of the
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second partial of the wavetable?
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<P>
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</LI>
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<LI>A sinusoid is stored in a wavetable with period 4 so that the first four
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elements are 0, 1, 0, and -1, corresponding to indices 0, 1, 2, and 3. What
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value do we get for an input of 1.5: (a) using 2-point interpolation? (b)
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using 4-point interpolation? (c) What's the value of the original sinusoid
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there?
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<P>
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</LI>
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<LI>If a wavetable's contents all fall between -1 and 1 in value, what is the
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range of possible outputs of wavetable lookup using 4-point interpolation?
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<P>
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</LI>
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</OL>
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<BR>
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<B> Next:</B> <A NAME="tex2html1117"
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HREF="node40.html">Audio and control computations</A>
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<B> Up:</B> <A NAME="tex2html1111"
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HREF="node26.html">Wavetables and samplers</A>
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<B> Previous:</B> <A NAME="tex2html1107"
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HREF="node38.html">Automatic read point precession</A>
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<B> <A NAME="tex2html1113"
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HREF="node4.html">Contents</A></B>
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<B> <A NAME="tex2html1115"
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HREF="node201.html">Index</A></B>
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<ADDRESS>
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Miller Puckette
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2006-12-30
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