This summer I have noticed a rise in people speaking extremely loudly with their speakerphones on. I am a big believer in each to his own but I experienced an awful episode on a bus where there were at least 6-7 people all speaking on their phones and one with a disgustingly booming voice was sat next to an elderly woman who had no headphones to drown him out. I felt so bad for her that I asked him to tone it down. He did but not by much.
What can be done to make inconsiderate individuals keep it down on public transport, aside from buy a car and stay clear. My only issue with this, is as you get older you may need to give up driving.