Place it as the reaction beat right after the reveal in your edit, preceded by a sudden suspense sting to build the moment, then follow it with a short huh for a second take from another character.
關於此聲音
A short Spanish voice clip, about one second long, of a speaker saying 'yo no lo sabía', meaning I did not know that. It gives a surprised, slightly sheepish feeling, like being caught off guard by new information you should probably have known already, and it lands as an honest admission rather than an excuse.