Many times people with PTSD and TBI can be sensitive to sounds. I have continued to be sound sensitive, but find ways to cope when it gets too much. One of the most difficult sounds for me is beeping or buzzing noises. Grocery stores are the worst for sounds like that and waking up to an alarm clock that beeps or buzzes can set me off track for the entire day.
About ten years ago I got an alarm clock that eliminated starting my day feeling like I was being ripped out of my sleep. It is a light progression clock called "Peaceful Progression". I consider it the "Cadillac" of alarm clocks because it is expensive, but also one of the best investments I made for my PTSD.
It uses light progression, but it also has a variety of other kinds of sounds, as well as, scent to wake up to. I don't always use the scent, but it's amazing how easy it is to wake up gently to light and your sense of smell.
I've met a lot of people living with PTSD that are heavy duty dreamers. We are often reliving these traumatic experiences in our sleep and to wake up hearing the jarring, sudden buzzing and whirring of an alarm clock doesn't make for a great start to the day.
Little changes in a person's day to day living can make a big difference. This is one of those things that has helped me.