Australian Open crowds have a well-worn reputation as some of the most boisterous in tennis, but even by that standard their latest antics have left players and viewers baffled and irritated in equal measure.
The tournament, already mired in controversy after star Novak Djokovic was detained and deported, is now drawing attention because crowds have adopted a Cristiano Ronaldo chant which sounds a lot like booing to use on players.
Fans are in fact shouting 'siuuuu' - based on the Spanish 'si' which Ronaldo and his fans shouted whenever he scored at Real Madrid - which has created a hostile atmosphere at Melbourne Park that has already begun to wind up athletes.
Nick Kyrgios told the crowd they were 'a zoo' after his first match in which the chant was frequently used, adding: 'I don't know what I've done to this crowd. You guys are out of control'.
'Siuuuu,' they responded.
And former No.1 Andy Murray also expressed his displeasure, revealing fans even used it during one of his practice sessions. 'It's incredibly irritating,' he said.
Nick Kyrgios is just one of a number of players to have been confronted with chants of 'siuuuu' at the Australian Open, comparing the crowd to 'a zoo'
Australian crowds are already known for being among the most boisterous in tennis, but have managed to draw attention for their boo-like chanting at this year's Open
Speaking to reporters after his first round victory against Briton Liam Broady, Kyrgios added: 'I can't believe they did it so much.
'They were doing some Ronaldo thing, Ronaldo does it every time he scores. I though they were going to do it for, like, ten minutes.
'They did it for two and a half hours.'
Opponent Broady described the atmosphere as 'absolutely awful' - revealing that, in addition to the Ronaldo chant, he also had to deal with 'sledging' from the sidelines.
Seemingly unaware of the Ronaldo connection, he said: 'It's the first time I've ever walked on to a tennis court and been booed, which for me was a crazy experience.
'You get sledged from the sides like you can't believe that doesn't get picked up on TV. So it was a very, very difficult atmosphere to try and handle.'
The atmosphere may have shocked players, but it perhaps less surprising when viewed against the backdrop of a contentious election in Australia and crumbling Covid response, off the back of some of the harshest lockdowns on the planet.
Melbourne, where the tournament is being held, has been particularly hard-hit - suffering for 262 days under one of the world's longest lockdowns last year.
That was followed by a vaccine roll-out that was criticised for being too slow, and which failed to stop Covid cases from soaring to record levels as Omicron arrived.
Andy Murray was also met by roars of 'siuuu' from crowds, revealing the
