The cone of silence based on the Wireless Mesh Network

The motivation can be described as followings:

I like to go to restaurants that are alive and happening. But often I find that the crowd noise makes it so I can't hear the person I'm sitting next to.

The Cone Of Silence is a small electronics product that you can bring to dinner in your pocket, place on the table, and create a "noise cancelled zone" around the table you and your friends are sitting at.

With the Cone Of Silence, you'll still get the feeling of being in a lively environment but you'll be able to hear your friends like they were in your home for dinner.

The Cone Of Silence uses active noise control technology (http://en.wikipedia.org/wiki/Active_noise_control) to create the appropriate interference with the crowd noise in the restaurant.

Key attributes of the product are size (compact), cost (below $150), and battery powered. The batteries will be rechargeable like a cell phone and the battery life should be at least three hours.

We can design a virtual room just for communicate with each other in voice based on Wireless Mesh Networks.
Headset using in car when you are driving can be introduced here, Here we should consider about these issues carefully:

1/ How can select the voice input so that nearby users can speak to the device.

2/ How to make listener feel comfortable just like without headset?

3/ How to be secure of voice?

4/ How to manage the spectrum?