239 lines
8.7 KiB
HTML
239 lines
8.7 KiB
HTML
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<!doctype HTML public "-//W3C//DTD HTML 4.0 Frameset//EN">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
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<meta name="generator" content="Adobe RoboHelp 9">
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<title>Ambient noise compensator</title>
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<link rel="StyleSheet" href="HtmlHelp.css" type="text/css">
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<style title="hcp" type="text/css">
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<!--
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span.hcp1 { font-weight:bold; }
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p.hcp2 { margin-bottom:0; }
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-->
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</style>
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</head>
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<body class="ns-0 ltr">
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<div id="globalWrapper">
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<div id="column-content">
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<div id="content">
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<h1 class="firstHeading">Ambient noise compensator Gap</h1>
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<div id="bodyContent">
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<p id="siteSub"><span style="font-style: italic;"> </span><img src="ANC_Gap.jpg" alt="" style="border-width: 2px; border-style: solid;" width="172" height="47" border="2"></p>
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<p>Allows the level of an announcer (or other programme
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material) to 'ride' on the average background (ambient)
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noise level so that the programme is kept at an audible
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level above that of the ambient noise.</p>
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<p>It does this by measuring the level of the ambient noise
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(using a suitably placed microphone), and controlling
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the gain of the programme channel accordingly.</p>
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<p>Since the gain must be controlled only by the ambient
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noise, and not by the level of the programme itself, the
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ambient signal level will only be measured and the gain
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adjusted during periods of inactivity in the programme
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channel.</p>
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<p>The length of the gap in programme required for sampling
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to occur is adjustable to allow for reverberation on the
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programme.</p>
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<p>Various controls further allow the user to vary the
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announcement threshold level for gap detection, the minimum
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and maximum applied gain, the speed of gain change, and
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the reference ambient level.</p>
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<h2> </h2>
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<h2>Inputs and Outputs</h2>
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<p>Announcement (Programme) input</p>
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<p>Ambient input - labelled 'Ambient'</p>
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<p>Audio output</p>
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<p> </p>
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<h2>Control Panel</h2>
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<p><img src="Anccp.jpg" alt="Image:anccp.png" title="Image:anccp.png" style="border-width: 2px; border-style: solid;
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margin-top: 0px; margin-bottom: 0px; margin-left: 0px;
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margin-right: 0px;" width="561" height="282" border="2"></p>
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<p> </p>
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<ul>
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<li class="p"><p>(Ambient) <span class="hcp1">Threshold</span>
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control</p></li>
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</ul>
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<dl>
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<dd class="mvd-P">Adjusts the ambient signal level
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at which unity gain will exist.</dd>
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<dd class="mvd-P">The amount by which the announcement
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channel gain is increased is equal to the amount by
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which the ambient level exceeds this threshold.</dd>
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<dd class="mvd-P">Lower threshold settings will tolerate
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lower ambient signal levels before increasing the
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announcement gain.</dd>
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<dd class="mvd-P">To lift the announcement out of the
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ambient noise more, reduce the setting of this control.</dd>
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</dl>
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<p> </p>
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<ul>
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<li class="p"><p><span class="hcp1">Ambient
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Level Meter</span></p></li>
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</ul>
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<dl>
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<dd class="mvd-P">Displays the current ambient noise
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level. It's positioning next to the Threshold control
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shows the difference between the ambient level and
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the threshold, (which is equal to the applied gain).</dd>
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</dl>
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<p> </p>
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<ul>
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<li class="p"><p><span class="hcp1">Announcement
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gain meter</span></p></li>
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</ul>
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<dl>
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<dd class="mvd-P">Indicates the current announcement
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channel gain. This also operates when the ANC is bypassed
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giving a visible indication of what the applied gain
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will be when bypass is disengaged.</dd>
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</dl>
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<p> </p>
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<ul>
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<li class="p"><p><span class="hcp1">Min
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Gain</span> control</p></li>
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</ul>
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<dl>
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<dd class="mvd-P">Determines the minimum gain that
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will be applied to the announcement channel.</dd>
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<dd class="mvd-P">This should be set (with the aid
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of the Min Gain button) during quiet ambient levels
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so that an adequate announcement level is obtained.</dd>
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</dl>
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<p> </p>
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<ul>
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<li class="p"><p><span class="hcp1">Min
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Gain</span> button</p></li>
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</ul>
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<dl>
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<dd class="mvd-P">Forces the gain to the minimum setting
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for set-up purposes.</dd>
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<dd class="mvd-P">Illuminates when activated.</dd>
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</dl>
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<p> </p>
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<ul>
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<li class="p"><p><span class="hcp1">Max
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Gain</span> control</p></li>
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</ul>
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<dl>
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<dd class="mvd-P">Determines the maximum gain that
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will be applied to the announcement channel.</dd>
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<dd class="mvd-P">This should be set (with the aid
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of the Max Gain button) during high ambient levels
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such that sensible operating levels, free of distortion
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etc. are maintained.</dd>
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</dl>
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<p> </p>
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<ul>
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<li class="p"><p><span class="hcp1">Max
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Gain</span> button</p></li>
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</ul>
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<dl>
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<dd class="mvd-P">Forces the gain to the maximum setting
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for set-up purposes.</dd>
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<dd class="mvd-P">Illuminates when activated.</dd>
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</dl>
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<p> </p>
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<ul>
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<li class="p"><p><span class="hcp1">Speed</span>
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control</p></li>
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</ul>
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<dl>
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<dd class="mvd-P">Determines the speed at which the
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gain will change. Obtrusiveness will be minimised
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at slower speed settings, although responsiveness
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to sudden changes in ambient level will be reduced.</dd>
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</dl>
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<p> </p>
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<ul>
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<li class="p"><p><span class="hcp1">Gap
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Time</span> control</p></li>
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</ul>
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<dl>
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<dd class="mvd-P">Determines the amount of time the
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announcement channel must be 'silent' in order for
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the ambient channel to be sampled.</dd>
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<dd class="mvd-P">In highly reverberant environments,
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a long gap time may be required to avoid false gain
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changes because of measuring the reverb tail of the
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announcement, rather than the ambient noise level.</dd>
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<dd class="mvd-P">Use the Ambient Meter as a guide
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to how quickly the signal dies away after an announcement
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ends.</dd>
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</dl>
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<p> </p>
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<ul>
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<li class="p"><p><span class="hcp1">Gap
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Threshold</span></p></li>
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</ul>
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<dl>
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<dd class="mvd-P">Determines the announcement input
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signal level below which the announcement channel
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signal must drop before it is considered to be in
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a gap, and thus allow ambient level sampling.</dd>
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<dd class="mvd-P">Try setting the Threshold control
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10dB or so above the idle noise of the announcement
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channel.</dd>
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</dl>
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<p> </p>
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<ul>
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<li class="p"><p><span class="hcp1">Gap
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LED</span></p></li>
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</ul>
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<dl>
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<dd class="mvd-P">Informs the user when there is an
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announcement gap that is allowing ambient signal sampling
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to take place.</dd>
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</dl>
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<p> </p>
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<ul>
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<li class="p"><p><span class="hcp1">Bypass</span>
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button</p></li>
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</ul>
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<dl>
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<dd class="mvd-P"><p class="hcp2">Removes
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the processor from the signal path.</p></dd>
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<dd class="mvd-P">Use bypass to set up the nominal
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announcement level.</dd>
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</dl>
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<p> </p>
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<h2>Notes</h2>
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<p>The ambient microphone should be connected to an analogue
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input on a BLU-80 or BLU-16 Signal Processor.</p>
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<p>The input gain should be adjusted to achieve a sensible
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operating level.</p>
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<p>When setting the Ambient Threshold control, the input
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gain should be taken into account.</p>
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<p>The Ambient microphone should be positioned clear of
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non-representative sources of sound and, to prevent tampering,
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preferably a place not accessible to the public.</p>
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<p>In a large environment, several microphones could be
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used with a mixer object in Soundweb to get an average
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of the levels.</p>
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<p><span class="hcp1">!</span> This object
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is capable of raising signal levels beyond the clipping
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point, so care should be exercised when using positive
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Maximum Gain values.</p>
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<p><span class="hcp1">!</span> It is recommended
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that a Limiter be used on the output of the Ambient Noise
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Compensator so that short term high-level signals are
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not allowed to pass through to the output.</p>
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<div class="editsection" style="float: right; margin-left: 5px;">
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<p> </p>
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<p> </p>
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</div>
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</div>
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</div>
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</div>
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</div>
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<p class="hcp2"> </p>
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</body>
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</html>
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