When Mt. St. Helens blew up I lived over 200 miles away in a tiny town called Newhalem, WA, in the North Cascades National Park. I heard the explosion but it sounded muffled & more like someone banging hard on the walls of the house. I yelled at my son (8 yrs old then) to stop banging on the walls. He was always into mischief so it made sense to me that it was his fault. haha He swore he didn't do anything & a few minutes later I heard on the tv that Mt. St. Helens had exploded. I couldn't believe that we'd hear it when we were so far away. Later some scientists explained that because of all the mountains in between that the sound bounced off & echoed all around Washington & Oregon with some living far away like we did hearing it loud & clear while others much closer didn't hear a thing.
Now I live right between Mount Baker & Glacier Peak - both of which are active volcanoes in the "very high threat" category. Washington state has 5 active volcanoes in that category - Mt. Baker, Glacier Peak, Mount Rainier, Mt. St. Helens & Mount Adams. Oregon also has 5 & California has 3.