Untitled Sighting

In the distance a loud "howl" like sound was heard. At first we thought maybe a bear had been hit by a car. Each "howl" lasted approx. 15 seconds. After the 3rd or 4th time another sound began echoing around the walls of the valley we were in. The closest thing I can  think of is someone speaking backward English through a megaphone. This lasted for around 5 minutes. The entire time none of us could make out a single word. Yet it sounded English. We basically figured that it was a crew of people looking for the animal making the first howl. Even though it was obvious that the original sound came from miles away. The first "howl" sounded very similar to a recording I heard on a page linked to BFRO's homepage.