What is the cheapest/convenient way to isolate a mobile phone from recording with microphone?
- The cellphone has to stay in the room, I can't put it outside
- Maximum 100$ solution
- Must not take more than 30 seconds to put in and out of the container
- Three cellphones have to fit in
- Tiniest as possible
- Can't dismantle the device
I've thought about putting the telephone in a container full of sand, sand is use in South America by narcotic gangs to acoustic proof a room occupied by a prisoner. But it sounds inconvenient to put the phone in a plastic bag to protect it from the sand and dig a bit each time you want to isolate it.
UPDATE: Some ways to solve this problem:
- Interference: Generating white noise through an application run by a phone in the box can work. The problem is that white noise can be removed quite easily. What might work is generating random noises inside the container.
- Saturation: There's probably a sound level for the microphone that makes any sound recovery impossible, saturating the input.
For both of those techniques, a closed box is needed (at least to prevent sound recording in the room).