WHEN DOES free speech become a pain in the head? When it is broadcast at over 85 decibels, according to the Tokyo metropolitan government, which is debating a law to curb noise pollution.
When does free speech become stifled? When loudspeakers are limited to 85 decibels, say right-wing and left-wing groups, who point out that average background noise on Tokyo's busy streets is about 80 decibels.
And so the stage is set for a showdown. On one side are Tokyo's local lawmakers who want to reduce the headache quotient in this city of 11 million people. On the other is an alliance of extreme right-wingers and their enemies, the communists, who both cruise the streets in 'sound trucks' with large loudspeakers blasting out their propaganda messages.
Most Japanese ignore the sound trucks, with their vitriolic attacks on communism, US neo-imperialism or the threat to Japan's rice farmers. So to maximise their exposure, the radicals turn up the volume and head for the most crowded points of the city: Shinjuku station, the busiest station in the world, which handles some 2 million passengers every day, or the main crossroads in Shibuya shopping district and the Ginza. Some right-wing groups specialise in noise barrages outside the Russian embassy, whose long-suffering diplomats must spend most of their working day wearing ear-plugs.
Shunichi Suzuki, the governor of Tokyo, is pushing a law which would limit the volume of loudspeakers to 85 decibels, as measured at a distance of 10 metres. The law would allow police to enter and search premises or vehicles thought to be violating the sound barrier.
'We are strongly against this new law,' said Atsushi Yamamoto, a local assembly member of the small People's Party. Mr Yamamoto was standing in front of his party's sound truck at Sukiyabashi crossing in the Ginza yesterday, and had to raise his voice above his colleague's speech condemning the country's latest political scandal.
In a country where the credibility of the political system is not particularly high, Mr Yamamoto says objectors like him must take to the streets to get their message across. 'If you speak out on the street, lots of people can listen'.
Meanwhile Kunio Suzuki, a right-wing nationalist, says the new law could start a dangerous process: 'If the police do not allow them to express their thoughts, the right-wingers could go underground.' The streets of Tokyo will get even more noisy this autumn, as right- and left-wing extemists protest against the new law from their sound trucks.