Phase Cancellation: Difference between revisions
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Phase (cancellation, interference) | Phase (cancellation, interference) | ||
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=== Theoretical Discussion === | === Theoretical Discussion === | ||
Running two inputs 180° out-of-phase puts the peaks and valleys of the sine wave so that they null each other out when summed (see the middle picture below). This has a tendency to cancel out both inputs, and is quite pronounced in the "far" field, but negligible in the "near" field. Normally phase cancellation is undesirable, but when you know what you want (and in this case, what you don't want) then you do it deliberately. | Running two inputs 180° out-of-phase puts the peaks and valleys of the sine wave so that they null each other out when summed (see the middle picture below). This has a tendency to cancel out both inputs, and is quite pronounced in the "far" field, but negligible in the "near" field. Normally phase cancellation is undesirable, but when you know what you want (and in this case, what you don't want) then you do it deliberately. | ||
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<EMBED src="http://www.sfu.ca/sca/Manuals/ZAAPf/splash/phase_diagram.spl" width=490 height=174 | <EMBED src="http://www.sfu.ca/sca/Manuals/ZAAPf/splash/phase_diagram.spl" width=490 height=174 | ||
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The illustration above is from [http://www.sfu.ca/sca/Manuals/ZAAPf/p/phase.html Phase at SFU]]. Follow the link for a very interesting discussion about Phase. | The illustration above is from [http://www.sfu.ca/sca/Manuals/ZAAPf/p/phase.html Phase at SFU]]. Follow the link for a very interesting discussion about Phase. | ||
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[[Image:PhaseIn.png]] | |||
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# Poor imaging | # Poor imaging | ||
See: [http://www.livesoundint.com/archives/2003/july/phase/phase.php Practical Realities of Phase Interference] | See: | ||
There is an interesting visual presentation of [https://www.youtube.com/watch?v=D7aftTF--5w how phase cancellation occurs with two sound sources]. | |||
[http://www.livesoundint.com/archives/2003/july/phase/phase.php Practical Realities of Phase Interference] | |||
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See: [[:Category:Phase|Phase]] | See: [[:Category:Phase|Phase]] | ||
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