Is it possible to completely disable voice chat in-server?

I have some TF2 servers, but I don't want voice chat to be enabled in certain servers. For example one of the servers is an achievement server running the achievement_idle map and due to its nature, I don't want voice chat to be enabled (due to the fact that these servers are there so that players can idle, not talk).

Another reason for this is that 95% of the time on other servers, voice chat seems to be overrun by kids who think a good idea of fun is to shout at anyone who kills them/general abuse. As a 'mature' adult, this is something I don't really want happening on my servers.

I have tried the following, with nothing working to disable voice chat:

• CVar: voice_enable 0 (does nothing as far as I can see);
• Simply requesting not to use mics (doesn't work, as the message is simply ignored);

As there is cl_voice 0 command, is there an equivalent server command (i.e, sv_voice 0?)? I also have not tried sv_allow_voice_from_file yet, but it doesn't seem to be what I want.

I also host a TeamSpeak3 server, which I encourage players to use (as it is far superior to TF2's voice chat feature in many ways); if players really want to use voice chat, they can use the TS3 server to do so.

Is it possible at all to disable voice chat, server-side?