'If you're in the zone and you're one of the sensitive people, you'll get headaches, nausea, tinnitus and ,' Leighton said. 'So it dawned on me that we were putting ultrasound into public places where a minority but a large number of people are going to be affected.' 'These are places where you might have a footfall of 3 or 4 million people a year,' he said. While he couldn't hear the sounds, he recorded them using his microphones and consistently found ultrasonic frequencies. Leighton started his early work on ultrasonic waves by going to buildings where people reported having symptoms. But most acoustical researchers just aren't studying high-frequency sound in human spaces when Live Science reached out to a number of acoustics experts outside Leighton's immediate circle of colleagues for comment on this article, the vast majority said they didn't have the knowledge to comment. That isn't to say that Leighton's work is outside the scientific mainstream he was one of two co-chairs of an invited session on high-frequency sound at the ASA meeting and has received The Royal Society's Clifford Paterson Medal for separate research into underwater acoustics. 'And that's, I think, why many sufferers ended up at my door.'

'I think you'd be lucky to find even six people around the world working on this,' Leighton said.

Headset making high pitched noise