do you know if is possible do some commands at sys.txt to the overspeed sound not be continuous? the main idea is overspeed sound be equal approach beep sound, the frequency of sounds occur by distances
for spoken warnings (tts) the command "overspeed_min_speech_repeat_delay=10" will set the fequency (in this case 10 seconds) at which the overspeed warning is repeated.

This might work for for the beep as well; if not you could try "overspeed_min_sound_repeat_delay" or even "overspeed_min_beep_repeat_delay"

Please reply if any of these ideas work