[sci.electronics] Low environment noise `killer'

shin@udel.edu (Jeong-Gyun Shin) (03/23/91)

Once I read an article (even though I don't remember exactly where)
about a device which emits opposit harmonics of noise from the environment
so to `cancel' the noise.  Supposingly this device was more effective against 
low and constant frequency noise such as noises from machines (for example,
low and constant humming of computing machinery room).  Does anyone know 
anything about it or had experience with such a device (How effective it is 
and so on)?  If so, can someone e-mail me where to get it and the price?  And, 
excuse-me if this post is inappropriate in this newsgroup (Do me a favor of 
redirecting me to an appropriate group?).

Thanks for any and all responses.

--
* Jeong-Gyun Shin, Newark, Delaware (shin@huey.udel.edu).