Many people associate recent strange sounds, booms, chemtrails, lights in the sky and similar events to the HAARP (High Frequency Active Auroral Research Program) which is US military project with the main facility located in Alaska (see photo). There are many conspiracy theories and even officials (in US and Europe) appear to concern about the project activities which may have different environmental effects.
Here are two old videos (back in 2007) from the CBC News broadcast in which the HAARP project is discussed in details. Please note that these videos were made before the vast majority of strange 2011-2012 events start to happen.
More official and unofficial details about HAARP might be found in the Wikipedia article.