If you watch video footage of urban emergency events that include sound, like 9/11, you notice the constant stream of sirens. If they are that loud on tape imagine how it must be on the ground.
You could be really glad you packed a couple sets of disposable ear plugs in your Urban Survival Bag for a couple of reasons.
First, you might just have to walk across the whole city to get home. Your day is going to be bad enough, and with the sirens running all day as they will be, it would be nice to be able to hear yourself think. Not only for the quiet, but also because it might help you calm down and be able to assess the situation better.
Sirens are a psychological trigger for emergency and they could cause unneeded anxiety at a time when you need to be thinking clearly about every move you make.
Secondly, what if you are purposely going to be staying in the area for an extended period of time? If you have assessed the situation and determined that you are not in immediate danger you may want to stay and help rescue others.
Ear plugs are one of the little things no one will be thinking about, but if you going to spend the next 8 to 12 hours digging people out of rubble with a couple hundred fire trucks and ambulances going by constantly they could really make things easier.