I agree with this, but there's a difference between someone having a real acoustic trauma and being exposed to 55 dB for 2 hours. Most stuff in life is higher than this threshold. For example, people go flying all the time with tinnitus, and an average flight is around 79 dB LAeq on some planes (that's about 59 dB or less with plugs). I know the cinema example has been used a lot recently, well what's the difference? Real acoustic traumas involve energy that is orders of magnitude higher than these levels. Like around 10,000 + times more power, depending if it's an impulse noise or sustained exposure to something more moderate, this number can go up or down.
To put it another way, if one has a job they will be exposed to more than 55 dBA every single day of their life. You cannot leave your house without this happening.