This sleep disorder called exploding head Syndrome is a very rare form of auditory hallucination.
It is a parasomnia in which subjects experience a loud bang in their head similar to the explosion of a bomb, a cymbal clash, the ringing of a bell or an earthquake. The sound is garbled and seems to come from inside the head.
This noise occurs at the beginning of sleep and although the sound is perceived as very high, it is usually not accompanied by pain. The syndrome causes anxiety in addition to a rapid heartbeat rate and heavy sweating.
No treatment has been found to date.