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out-of-phase ?? [Copy link] 中文

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Post time 2005-1-27 22:55:29 |Display all floors
Speakers that produce out-of-phase sound waves can then be put closer to the worker under the dest or the machine.

What's the meaning of "out-of-phase"??
thx~~

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Post time 2005-1-28 04:06:49 |Display all floors

out-of-phase sound waves are used for noise reduction

out-of-phase = unsynchronized

Sound travels in waves. Similar sound waves whose peaks (maxima) do not coincide are said to be out-of-phase. If the peaks of one coincide with troughs (minima) of the other, the two waves are said to be 180° out-of- phase.  This is the basis of "noice-cancellation" devices.

This site shows how two sound waves that are 180° out-of-phase cancel each other, and this results in noise reduction.
http://www.mediacollege.com/audio/01/wave-interaction.html

More about the physics of sound waves is at this site
http://hop.concord.org/s1/phys/s1p.html

Cheers!

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Post time 2005-1-28 07:42:50 |Display all floors

yes thats it

A sound wave has a length.  The music note A 440 is somewhere around 20 cm long.  If the A 440 is too loud compared to the volume of other mid-range sound, it is resonating, and you should move the speaker one or two cm forward or back.

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