# The Audio Laser Revisited

**URL:** <https://boards.straightdope.com/t/the-audio-laser-revisited/194206>\
**Category:** Cecil's Columns/Staff Reports\
**Created:** [August 10, 2003, 3:56pm UTC](https://boards.straightdope.com/t/the-audio-laser-revisited/194206 "2003-08-10T15:56:21Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![jovan](https://avatars.discourse-cdn.com/v4/letter/j/0ea827/32.png) [@jovan](https://boards.straightdope.com/u/jovan)\
**Post date:** [August 10, 2003, 3:56pm UTC](https://boards.straightdope.com/t/the-audio-laser-revisited/194206/1 "2003-08-10T15:56:21Z")

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So I was perusing the archive, and I chanced upon this elderly column: [http://www.straightdope.com/classics/a2\_114.html](http://www.straightdope.com/classics/a2_114.html)

In said article, Cecil roundly dismisses the idea of an “audio laser”.

[In this thread](http://boards.straightdope.com/sdmb/showthread.php?threadid=323) and [this thread](http://boards.straightdope.com/sdmb/showthread.php?threadid=261), the issue is further discussed.

All that info, however, is obsolete. The audio laser is, for practical purposes, a reality.

The [Audio Spotlight](http://www.howstuffworks.com/news-item190.htm), developed at MIT works a lot like an “audio laser”.

Meanwhile, the [Hypersonic Sound System](http://www.atcsd.com/tl_hss.html) creates much the same effect as the audio spotlight.

And furthermore, there’s a Japanese company (damn I can’t remember which one…) that’s putting out their own technology on the market to do the same thing.

So, in short, not “audio lasers” strictly, but stuff that behaves a lot like it is being put on the market.

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**Author:** ![The\_Ryan](https://avatars.discourse-cdn.com/v4/letter/t/7feea3/32.png) [@The\_Ryan](https://boards.straightdope.com/u/The_Ryan)\
**Post date:** [August 11, 2003, 5:31am UTC](https://boards.straightdope.com/t/the-audio-laser-revisited/194206/2 "2003-08-11T05:31:53Z")

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A laser is more than just a tightly focused light beam: it is a collection of photons all in phase and of the same polarization. There is no audio counterpart because sound doesn’t have polarization. I don’t know why that wasn’t mentioned in the column.

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**Author:** ![jovan](https://avatars.discourse-cdn.com/v4/letter/j/0ea827/32.png) [@jovan](https://boards.straightdope.com/u/jovan)\
**Post date:** [August 11, 2003, 6:09am UTC](https://boards.straightdope.com/t/the-audio-laser-revisited/194206/3 "2003-08-11T06:09:43Z")

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Of course, which is why I said that the stuff above is not “strictly” a laser. I just thought it was cool and worthy of mention.

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**Author:** ![rowrrbazzle](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rowrrbazzle/32/414_2.png) [@rowrrbazzle](https://boards.straightdope.com/u/rowrrbazzle)\
**Post date:** [August 15, 2003, 7:07pm UTC](https://boards.straightdope.com/t/the-audio-laser-revisited/194206/4 "2003-08-15T19:07:02Z")

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A laser beam is not necessarily polarized. [http://electron9.phys.utk.edu/optics421/modules/m7/laser\_systems.htm](http://electron9.phys.utk.edu/optics421/modules/m7/laser_systems.htm)

> [@](#):
>
> In a simple helium neon laser with cylindrical symmetry, the output is said to be randomly polarized. Each individual cavity mode has a linear polarization at any one time. However, the overall laser output is a time varying mix of modes of different polarization. Consequently, the beam appears to be non-polarized when integrated over a fairly short period of time.
> 
> Although the beam intensity is fairly constant, if the experiment or application involves polarization dependent optics, such as beam-splitters, then large rapid amplitude fluctuations will be apparent. If this is not acceptable, a polarized helium neon laser must be used. A polarized helium neon laser has an intra cavity Brewster window which introduces sufficient loss in the s-plane of polarization (defined by the window) so that only p-polarized output is produced.