The loud boom you hear around the arenal volcano is caused by real estate sales. People love the lake arenal area...it is simply gorgeous living here overlooking the lake/volcano...my wife and I have been here for 17 years and life is as good as it can get in costa rica...we recommend family living around the lake on the north side because of the national forest which is located at the rear of most property sites...what a kick to discover wild animals in our yard and just an incredible number of wild birds...we found a heaven here.