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179 lines
5.7 KiB
179 lines
5.7 KiB
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original version by: Nikos Drakos, CBLU, University of Leeds
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HREF="node100.html">Two-cosine carrier signal</A>
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HREF="node97.html">Examples</A>
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HREF="node98.html">Wavetable pulse train</A>
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<H2><A ID="SECTION001052000000000000000">
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Simple formant generator</A>
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</H2>
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<P>
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The next three examples demonstrate the sound of the varying pulse
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width, graph its spectrum, and contrast the waveshaping pulse generator.
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Skipping to Example F05.ring.modulation.pd (Figure <A HREF="#fig06.14">6.15</A>), we show the
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simplest way of combining the pulse generator with a ring modulating
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oscillator to make a formant. The pulse train from the previous example is
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contained in the <TT>pd pulse-train</TT> subpatch. It is multiplied
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by an oscillator whose frequency is controlled as a multiple of the
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fundamental frequency. If the multiple is an integer, a harmonic sound
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results. No attempt is made to control the relative phases of the components
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of the pulse train and of the carrier sinusoid.
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<P>
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<DIV ALIGN="CENTER"><A ID="fig06.14"></A><A ID="6976"></A>
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<TABLE>
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<CAPTION ALIGN="BOTTOM"><STRONG>Figure 6.15:</STRONG>
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Excerpt from example F05.ring.modulation.pd combining ring modulation
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with a stretched wavetable pulse generator</CAPTION>
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<TR><TD><IMG
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WIDTH="352" HEIGHT="285" BORDER="0"
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SRC="img614.png"
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ALT="\begin{figure}\psfig{file=figs/fig06.14.ps}\end{figure}"></TD></TR>
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</TABLE>
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</DIV>
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<P>
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The next example, F06.packets.pd (Figure <A HREF="#fig06.15">6.16</A>), shows how to
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combine the stretched wavetable pulse train with a sampled sinusoid to realize
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movable formants, as described in Section <A HREF="node95.html#sect6.carrier">6.3</A>. The pulse
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generator is as before, but now the carrier signal is a broken sinusoid.
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Since its phase is the fundamental phase times the center frequency quotient,
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the sample-to-sample phase increment is the same as for a sinusoid at the
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center frequency. However, when the phase wraps around, the carrier phase
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jumps to a different place in the cycle, as was illustrated in Figure
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<A HREF="node95.html#fig06.07">6.7</A>.
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Although the bandwidth quotient <!-- MATH
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${\omega_b}/\omega$
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-->
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<IMG
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WIDTH="38" HEIGHT="32" ALIGN="MIDDLE" BORDER="0"
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SRC="img588.png"
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ALT="${\omega_b}/\omega$"> must be at least
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one, the center
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frequency quotient <!-- MATH
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${\omega_c}/\omega$
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-->
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<IMG
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WIDTH="38" HEIGHT="32" ALIGN="MIDDLE" BORDER="0"
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SRC="img587.png"
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ALT="${\omega_c}/\omega$"> may be
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as low as zero if desired.
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<P>
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<DIV ALIGN="CENTER"><A ID="fig06.15"></A><A ID="6986"></A>
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<TABLE>
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<CAPTION ALIGN="BOTTOM"><STRONG>Figure 6.16:</STRONG>
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Using stretched wavetable synthesis to make a formant with movable
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center frequency.</CAPTION>
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<TR><TD><IMG
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ALT="\begin{figure}\psfig{file=figs/fig06.15.ps}\end{figure}"></TD></TR>
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</TABLE>
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HREF="node100.html">Two-cosine carrier signal</A>
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HREF="node97.html">Examples</A>
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<B> Previous:</B> <A ID="tex2html2017"
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HREF="node98.html">Wavetable pulse train</A>
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<ADDRESS>
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Miller Puckette
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2006-12-30
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