Last year, a man in his 70s in Kobe in western Japan filed a lawsuit against a daycare centre in his neighbourhood.
He said he was being disturbed by sounds the children were making, and demanded the construction of sound barriers as well as monetary compensation for his suffering.
He claimed that the "noise" had exceeded the 60-decibel legal threshold in the area and, therefore, must be regulated by law.
"We try to address this problem, and close windows and curtains whenever we can," a spokesman of the daycare centre told the Mainichi Shimbun in an interview. Installing sound barriers might not be a good solution. They are expensive and also block out sunlight.
About a month later, another man, this one in his 40s and from western Tokyo, was arrested for using a hatchet to threaten a father who was at a daycare centre picking up his child. The man felt that the kids were too noisy.
Daycare centres in about 70 per cent of Tokyo municipalities have received complaints about noisy children, according to the Tokyo Metropolitan Government.
A survey by Yahoo! Japan last October revealed that 49.4 per cent of respondents had been annoyed by noisy children while the rest had not.
In addition to noise from children, residents also complained about that from parents as well as the sound made by musical instruments, car and bicycle traffic and parking. As a result, municipal governments in Tokyo are having difficulties in obtaining consent from local communities when they try and find appropriate real estate for new daycare centres.
Actually, this issue started to attract public attention in 2007, when a woman in her late 60s won a case over children's noise against a municipal government in Tokyo. She felt that children playing in a public park's water fountain were too noisy, and demanded that the fountain be turned off.
Based on the assessment that the children's voices had exceeded the area's legal limit, the district court issued a controversial provisional injunction ordering the city to turn off the fountain.
This case seems to have encouraged other local residents facing similar problems to bring these matters to court.
By the end of last year, it had become clear that it was high time for Japan as a society to decide whether it should regard children's noise as just one type of sound or something qualitatively different.
What accounts for this reaction against noisy children?
The answer is a changing socioeconomic environment.
First, more women are entering the workforce, and demand for childcare centres has soared.
Between 2004 and 2014, the number of working women in Japan rose by over one million while that of working men fell by more than 900,000. The labour force participation rate of women aged between 25 and 34 went up from 63.6 per cent to 71.6 per cent in the same period.
As a result, 2.37 million pre-school children are now spending week days at daycare centres, up from 1.97 million in 2004, and the number is growing.
To accommodate this, more than 1,000 daycare centres have been newly made available in the past five years, many of them conveniently located for working mothers in residential areas. Even so, more than 40,000 children were still waiting for openings as of last October.
Second, there is a much larger number of people staying at home in the day compared to the past. Japan is rapidly ageing and baby boomers are retiring. Right now, 26.3 per cent of Japanese citizens are aged 65 and above, of whom only 20.8 per cent are working.
Many of them stay at home and naturally get to hear the sound of small children chatting, singing, clapping and dancing throughout the day.
Major cities in Tokyo have high population density of more than 10,000 per sq km. Toshima city's population density is 22,569 per sq km, almost triple that of Singapore's 7,615. If you live next to a daycare centre in one of these cities, you hear everything.