I added my opinion to the official bug forum thread concerning the "new" sounds that are coming from my warhorn after the Tuesday patch. About 5 hours ago, I received a message:
The thread "Warhorn sounds wrong" was moved from "Bugs: Game, Forum, Website" because it was a better fit for the "Guild Wars 2 Discussion" sub-forum.
This move seems to indicate that it was an intentional change, and Anet does not consider it to be a bug (I guess they intend for it to sound like a Norn with digestive problems). They also merged several threads together, under the name "Warhorn Audio Feedback [merged]".
Nobody from ArenaNet has commented on the thread, as of this time. I will keep watching, and will update here with any news.