My mother used to be a police officer, and she once came back from a visit to the department of the interior in our federal state (of Germany) and told me about a room they had there (maybe several) for meeting where sensitive issues are discussed. What sets them apart - among other things, I guess - is that there are no phone lines, no network, and for meetings people are not allowed to bring telephones/smartphones, tablets, or computers of any kind.

So, yes, the audio thing is something to worry about.