Try Ativan. It is fast acting, the sublingual type. The other posters have confirmed, myself included, that it may be tough to stop the panic attacks when waking up with loud T in the first few months. ?I myself used mental imagery technique to minimize the fear for this ringing sound. Check my success story for detail of it.
Since when T is new, it is natural to wake up with panic,
try to accept your condition instead of fearing it more. Acceptance is a powerful technique. If needed, use quick acting Ativan to subdue the effect of the panic attack. Panic attack is alarming and uncomfortable with symptoms like hard attack. But it is not going to kill us. I know this beast well. I lived with it for decades. Actually the skills I learn since T, the CBT, mindfulness, etc., have helped reduce the attack. I just learn the paradoxical approach towards panic attack by inviting it, the mindfulness approach by facing and embracing it instead of running away from the symptoms. Don't fear the panic attacks. They will slowly reduce in frequency and intensity. You can say something like 'ok, an attack is on, but I am going to face this sensation instead of running from it. I accept I have a hard time doing that now, but like others say, it will get better. I am not going to provide more fuel to T if I can.' In all the years living with anxiety/panic disorder, I have learned that acceptance and the paradoxical approach to invite the symptoms are very effective ways to reduce the frequency and intensity of the attacks.