Polish radio (Program 1) brodacasted (and maybe still does) a time signal at 12:00 every day. It's a series of beeps and the end of the last and the longest beep marks 12:00. Here's how it sounds:

https://www.youtube.com/watch?v=p34LVMQI19M&t=129s

Fun fact, in the past (I suppose it's obsolete by now, since time and distance are defined in terms of the speed of light now) the carrier of the Program 1 (225kHz - as visible on the video) was an official standard of frequency in Poland.