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178 lines
5.3 KiB
178 lines
5.3 KiB
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original version by: Nikos Drakos, CBLU, University of Leeds
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* revised and updated by: Marcus Hennecke, Ross Moore, Herb Swan
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<TITLE>Exercises</TITLE>
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HREF="node40.html">Audio and control computations</A>
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<B> Previous:</B> <A ID="tex2html1378"
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HREF="node56.html">MIDI-style synthesizer</A>
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<!--End of Navigation Panel-->
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<H1><A ID="SECTION007110000000000000000">
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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>How many partials of a tone at A 440 can be represented digitally at a
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sample rate of 44100 Hertz?
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<P>
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</LI>
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<LI>What frequency would you hear if you synthesized a sinusoid at 88000 Hertz
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at a sample rate of 44100?
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<P>
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</LI>
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<LI>Suppose you are synthesizing sound at 44100 Hertz, and are computing
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64-sample audio blocks. A control event is scheduled to happen at an elapsed
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time of exactly one second, using the fast-as-possible update scheme. At what
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sample does the update actually occur?
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<P>
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</LI>
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<LI>Sampling at 44100, we wish to approximately play a tone at middle C by
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repeating a fixed waveform every N samples. What value of <IMG
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WIDTH="18" HEIGHT="14" ALIGN="BOTTOM" BORDER="0"
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SRC="img3.png"
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ALT="$N$"> should we
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choose, and how many cents (Page <A HREF="node11.html#eq-pitchmidi"><IMG ALIGN="BOTTOM" BORDER="1" ALT="[*]"
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SRC="crossref.png"></A>) are we off from the
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"true" middle C?
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<P>
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</LI>
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<LI>Two sawtooth waves, of unit amplitude, have frequencies 200 and 300 Hertz,
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respectively. What is the periodicity of the sum of the two? What if you
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then wrapped the sum back to the range from 0 to 1? Does this result change
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depending on the relative phase of the two?
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<P>
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</LI>
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<LI>Two sawtooth waves, of equal frequency and amplitude and one half cycle
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out of phase, are summed. What is the waveform of the sum, and what are its
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amplitude and frequency?
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<P>
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</LI>
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<LI>What is the relative level, in decibels, of a sawtooth wave's third
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harmonic (three times the fundamental) compared to that of the fundamental?
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<P>
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</LI>
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<LI>Suppose you synthesize a 44000-Hertz sawtooth wave at a sample rate
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of 44100 Hertz. What is the resulting waveform?
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<P>
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</LI>
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<LI>Using the techniques of Section <A HREF="node47.html#sect3.analog">3.7</A>, draw a block diagram
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for generating two phase-locked sinusoids at 500 and 700 Hertz.
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<P>
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</LI>
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<LI>Draw a block diagram showing how to use thresholding to detect when one
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audio signal exceeds another one in value. (You might want to do this to
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detect and filter out feedback from speakers to microphones.)
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<P>
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</LI>
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</OL>
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<P>
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<HR>
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<BR>
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<B> Next:</B> <A ID="tex2html1388"
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HREF="node58.html">Automation and voice management</A>
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<B> Up:</B> <A ID="tex2html1382"
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HREF="node40.html">Audio and control computations</A>
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<B> Previous:</B> <A ID="tex2html1378"
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HREF="node56.html">MIDI-style synthesizer</A>
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<B> <A ID="tex2html1384"
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HREF="node4.html">Contents</A></B>
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<B> <A ID="tex2html1386"
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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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</ADDRESS>
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