I thought this was something else... my cousin has been living in Japan 10+ years in a small town for on the other side of Mt Fuji from Tokyo and I went and stayed with him for a couple of weeks. Every day (maybe twice? I can't remember) loudspeakers on poles around the neighborhood would start playing amateurish announcements - some very old man half-asleep reading a list of events, news, etc. I was hoping they turned it digital and just sent it to your phone. For how peaceful things normally were in this town it was disruptive.
In Okinawa I get music in the morning when kids need to go to school as well as random announcements.
Japan has always been weird like that - people are generally quiet and respectful of others, but when it comes to trucks driving around blaring out political speeches, or a "pay to take your large trash" van playing music while driving around to advertise its presence, all bets are off.
Those can be anything from daily announcements telling kids to get home before dark, testing the emergency announcement system, reminding people about today's festival, or asking people to be on the look-out for 89-year-old Takahashi-san who was last seen at the vegetable stand earlier this morning.
That thing is an air raid siren. It's broadcast from city or town offices, and everyone believes it's for disaster mitigation. Sure, but they run complete human in loop system readiness tests each day every day. You don't need that level of assured reliability for those community announcements.
These systems are also there in case of earthquake or tsunami, where people have very short times to act before disaster strikes.
I was cycling around the Izu Peninsula earlier this year and one morning was woken up at 6am by the local ojisan on the PA system.
He wanted to tell everyone that tonight on TV there's an episode of a show with a scene filmed at the local beach. 6am!
Where I am there's now only some music at 17:00, ideally that should announce that it's time to leave work and go home, ffs.. but as this is Japan, it doesn't seem to serve a purpose - people don't go home. That music used to be a siren until a few years ago. I like the melody better.
We do get the aforementioned trucks driving around all day announcing loudly that they'll take your trash, for payment.. but it's very rare now. And the pole sellers seem to have disappeared entirely. I could use a new pole though.. for drying clothes. There has fortunately never been any political speech trucks around here. The town is too small I assume.