Code
if (!(_vehicle getVariable "siren2")) exitWith {};
if (count crew _vehicle isEqualTo 0) then {_vehicle setVariable ["siren2",false,true]};
if (!alive _vehicle) exitWith {};
if (isNull _vehicle) exitWith {};
_vehicle say3D "speech";//Class/name specified in description.ext
sleep 7;//Exactly matches the length of the audio file.
if (!(_vehicle getVariable "siren2")) exitWith {};
fertig