I don't now where you live, but there seam to be drastic differences between countries. These vehicle do have an in-city and out-city loudness. Also here they tend to have the siren off most of the time and only turn them on immediately before an intersection.
Funnily enough, I got into trouble in Korea (Jeju to be specific) because of this. I had just stopped at a red light (huge intersection), and I saw a police car get behind me, they had their lights on and put on the sirens.
In my home country (France), lights mean emergency, sound means "MOVE ITS URGENT" (and they generally ONLY use sirens when it is REALLY urgent). So when they started the siren, I put my warning lights on and moved slowly through the red light and to the outside of the road (I did not continue moving).
The guy ripped me a new one in Korean, but then I explained that I thought it was urgent because we were all stopped and they put the sound on so I moved out of the way in the safest way I could and even stopped. He calmed down eventually.
Apparently, it's normal in Korea for police cars to 1) always have the lights on and 2) just randomly blast the sirens going about their day.
I live in Paris, France and it’s so loud (but people here don’t really respect emergency vehicle so it could be part of why it’s so loud). In contrast, I spent a month in Tokyo Japan; and even though I was near a police station, it was nowhere near the sound level of what we have here. Curious what other countries you have in mind?
