The US embassy in Havana more than halved its staff in 2017 when diplomats complained of headaches, nausea and other ailments after hearing penetrating noises in their homes and nearby hotels.

The mysterious wave of illness fuelled speculation that the staff had been targeted by an acoustic weapon. It was an explanation that appeared to gain weight when an audio recording of a persistent, high-pitched drone made by US personnel in Cuba was released to the Associated Press.

But a fresh analysis of the audio recording has revealed what scientists in the UK and the US now believe is the true source of the piercing din: it is the song of the Indies short-tailed cricket, known formally as Anurogryllus celerinictus.

“The recording is definitively a cricket that belongs to the same group,” said Fernando Montealegre-Zapata, a professor of sensory biology at the University of Lincoln. “The call of this Caribbean species is about 7 kHz, and is delivered at an unusually high rate, which gives humans the sensation of a continuous sharp trill.”