I was looking at the specs in the first post and noticed the engine was a two cylinder - two stroke.
I thought that had to be very loud so I did some looking up.
The first ones were electric and quiet but too costly so they put a motorcycle engine in it.
Cheaper but much louder.
Here is a 7 minute video on Goliath from Tank Chats. (Tank Chats is a great series by the way)