During one of my last connections in DTW, an alarm went off and nobody knew what it was for, but it was loud. Thankfully, I had some ear plugs that helped drown out the noise. I carry the ear plugs, mostly to use on planes that do not have AVOD and there are crying babies, people talking on phones, people smacking their lips and things like that. Really helps calm my nerves. Now, if there is AVOD, my noise cancelling headphones work great.