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<a accesskey="3" href="page.php?w=Envelope_%28waves%29&amp;p=2">3.Next</a>
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<p>In <a href="page.php?w=physics">physics</a> and <a href="page.php?w=engineering">engineering</a>, the <b>envelope</b> of an <a href="page.php?w=oscillating">oscillating</a> <a href="page.php?w=signal">signal</a> is a <a href="page.php?w=smooth_curve">smooth curve</a> outlining its extremes. The envelope thus generalizes the concept of a constant <a href="page.php?w=amplitude">amplitude</a> into an <b>instantaneous amplitude</b>. The figure illustrates a modulated <a href="page.php?w=sine_wave">sine wave</a> varying between an upper envelope and</p><p>
<a accesskey="3" href="page.php?w=Envelope_%28waves%29&amp;p=2">3.Next</a>
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