I've had this a couple of times - first time was terrifying as I was a young teenager. Second time was quite recently, almost 35 years later. No idea what's ca

I've had this a couple of times - first time was terrifying as I was a young teenager. Second time was quite recently, almost 35 years later. No idea what's caused it at all - sounds like someone has suddenly opened a pressurised pipe near my head/ear.