Canceling it Out

I used to travel a lot and often had to stay in hotels right next to a freeway. I often lay awake nights wondering if active noise cancellation could be used to lower the noise. Perhaps a sensor on the window could be used for detection, and a PZT driver on the window to reverse the vibration? Or, maybe a small "cone of silence" could be set up right over the sleeper's head?

The "cone of silence" was a brilliant product concept - even though it didn't work in our favourite comedy.. I bet the 'hat of silence' idea would be a best seller - we have so many environments where noise is a problem. (but does it have to be cone shaped? ).

Actually the "cone of silence" was implemented for small aircraft pilots. I sat in a cockpit of a piper cub in Arizona one day. The engine noise was pretty bad with normal conditions, then a switch was thrown and the noise almost disappeared! When I moved my head a few inches to the sides, the noise would return.

Next, they placed a beaker of ink on a small shake table, and it threw ink all over the place. After another switch was thrown, the beaker went static, and no more ink was lost (even after refilling it). The rest of the shaker was still wildly vibrating!

The company that designed this was Noise and Vibration Engineering. They did not last, but the technology did work.

Impressive technology indeed.

It doesn't take much imagination to come up with a long list of workplaces where this would be a boon. Virtually anywhere that machines are used.

But as you pointed out, it's even more applicable where noise interferes with rest.

Just out of curiosity, would the "cone of silence" you tested in the aircraft also make it impossible to hear your co-pilot speak (as seen on Get Smart)?

No. The "cone of silence" has a time constant that it relies on to eliminate background noise. So any transient noise such as spoken words get through just fine. This effect can be observed with noise cancelling headphones. Put them on while driving your car, and ask a passenger to speak to you. You will hear him/her easily, but the road noise will be significantly diminished.

Then it's really ideal...

i love my noise-cancelling headphone. Uncanny silence with the mp3 pleayer disconnected.

Pity that i can't wear them when sleeping.

i am surprised that the pioneers of this technology haven't developed many more products.

Headphones are uncomfortable, and air travel is, for most people, only occasional, so how about an array of noise-cancelling speakers in the corners of a room, defining a "cube of silence?" Or two speakers built into or attached to the back of a chair and aimed at the user's ears?