http://www.ptsduk.org/hyperacusis-and-ptsd/
Hyperacusis is a condition that arises from a problem in the way the brain’s central auditory processing center perceives noise and is estimated to affect between 7% and 23% of the UK adult population. It can develop as a result of physical damage sustained to the hearing apparatus (through a head injury, Lyme disease, air bag deployment, Bell’s Palsy etc), or from conditions such as PTSD.
There is a confirmed link between PTSD and hyperacusis due to a cerebral processing problem specific to how the brain perceives sound and as you can imagine, when they are present concurrently have the potential to exacerbate one another. Hyperacusis is very different from the reduced tolerance for noise that most of us have when we’re tired or stressed, or reacting to an obviously unpleasant noise, such as someone scratching their fingernails down a blackboard.
People with with hyperacusis have difficulty tolerating sounds which do not seem loud to others, such as the noise from running water, sirens, a phone ringing, dogs barking, walking on leaves, a washing machine, laughter and shouting, and the vacuum cleaner – any sound can potentially trigger a reaction in someone with hyperacusis – even the sound of their own voice.