[mbell]

'Active Noise Canceling' in an open space isn't a reality. You can do it, in an anechoic chamber, with a massive array of microphones and an equally large number of speakers, and even then, you can often only target a particular area. It is completely irrational for a space like an airplane. His mention of a couple of speakers above your head, is particularly laughable. In an open space the best your going to do is sound masking, which is nothing more than shaped white noise to drown out the other sounds, aircraft engines already do a pretty good job of this with the exception that their frequency spectrum can be a bit annoying.

On the other hand, you can do structural vibration cancellation to reduce outside (engine, air) noise entering the cabin. This would be done using sensors/actuators on the inner structure of the cabin. A proposal was out to do this for the A380 but I don't know if it was actually included in the final design or not.

Additional points that caused a snicker:

> laser / ultrasonic zoning of noise, which I've seen some night clubs use.

I've read some research into creating noise barriers by using extremely focused sound, but in laboratories, certainly not in night clubs. Most notably the goal is to create a focused area of very high pressure using a phased array of sources. This pressure levels needed to create a 'barrier' would likely be damaging to a human ear entering the area. I have no idea where the ultrasonic nor laser idea is coming from.

> Noise suppression of the flush in the bathroom/restroom. I think the volume is too high to be safe.

The SPL level of an airplane toilet flush is a long ways away from being damaging. Annoying? sure. Damaging? not unless you have a condition that results in highly sensitive ear drums.