227 lines
9.0 KiB
HTML
227 lines
9.0 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>Non-Gap Ambient Noise Compensator</title>
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<!-- Head Scripts -->
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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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</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 Non Gap</h1>
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<div id="bodyContent">
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<img src="ANC_Non_Gap.jpg" alt="" style="border-width: 2px;
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border-style: solid;" width="172" height="47" border="2">
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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 dynamically measuring the level of the
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ambient noise (using a suitably placed microphone), and
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controlling the gain of the programme channel accordingly.</p>
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<p>When a change in applied gain occurs (due to a change
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in the ambient level), the rate at which the applied gain
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changes to the new gain is governed by the attack and
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release settings. The gain moves towards its new value
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exponentially.</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, it
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is important that the measurement microphone(s) used to
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generate the ambient level input should be placed away
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from the announcement/program speakers and should be directed
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towards the ambient noise source, otherwise the microphones
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will 'hear' the announcement/program material, rather
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than the true ambient noise and could therefore create
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a feedback loop, increasing the gain because they detect
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a rise in level (due to the increased gain), and so on
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until they hit the max gain.</p>
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<p> </p>
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<div class="editsection" border-style:="" border="0">
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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> <br>
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<img src="NGANC_panel.jpg" alt="Image:NGANC panel.jpg" title="Image:NGANC panel.jpg" style="border-width: 2px;
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border-style: solid; margin-top: 0px; margin-bottom: 0px;
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margin-left: 0px; margin-right: 0px;" width="585" height="321" 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
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by which the ambient level exceeds this threshold,
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multiplied by the ratio setting.</dd>
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<dd class="mvd-P">To lift the announcement out
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of the ambient noise more, reduce the setting
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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
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noise level. Its positioning next to the Threshold
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control shows the difference between the ambient
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level and the threshold.</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
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is bypassed giving a visible indication of what
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the applied gain 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
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aid of the Min Gain button) during quiet ambient
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levels so that an adequate announcement level
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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
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setting 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
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aid of the Max Gain button) during high ambient
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levels such that sensible operating levels, free
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of distortion 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
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setting 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">Ratio</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 ratio of the gain
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that will be applied to the announcement channel.
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At a ratio of 1:1, if the ambient level is 4dB
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over the threshold, the gain will be 4dB. If the
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ratio is 5:1, the applied gain will be 20dB. If
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the ratio is 0.1:1, the applied gain will be 0.4dB,
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and so on.</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">Attack
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and Release</span> controls</p></li>
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</ul>
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<dl>
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<dd class="mvd-P">Attack and release should be
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adjusted to allow the applied gain to track the
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ambient level for the given application. For example,
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fairly short attack and release times could be
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used on railway platforms to allow an announcement
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to quickly adjust as a train pulled into a station,
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whereas longer ballistics could be used in a stadium
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to gradually turn up announce levels as the stadium
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fills before a match.</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. Bypass overrides
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all controls and sets the gain to 0dB almost instantaneously.</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
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analogue 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
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input gain should be taken into account.</p>
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<p>The Ambient microphone should be positioned clear
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of non-representative sources of sound and, to prevent
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tampering, preferably a place not accessible to the
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public.</p>
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<p>In a large environment, several microphones could
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be used with a mixer object in Soundweb to get an
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average 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
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recommended that a Limiter be used on the output of
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the Ambient Noise Compensator so that short term high-level
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signals are not allowed to pass through to the output.</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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<p class="hcp2"> </p>
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</div>
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</body>
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</html>
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