There is a mysterious droning sound often described as like a diesel engine idling that is severely impacting the quality of life of 2 percent of people in places around the world. The thing is, no one knows what's causing it - or if it actually exists.Learn more about advertising on the HowStuffWorks podcasts at www.howstuffworks.com/advertisers.htmAnd to learn about your ad choices when listening to podcasts, visit https://www.howstuffworks.com/privacy.htm#ad-choices
