* Speech: If the announcement was made verbally, the concrete noun could be speech, pronouncement, or statement.
* Notice: If the announcement was written or displayed, the concrete noun could be notice, poster, flyer, bulletin, or sign.
* Broadcast: If the announcement was made over radio or television, the concrete noun could be broadcast, announcement, or news report.
Ultimately, the best concrete noun will depend on the specific type of announcement being made.