Good first pass would be decaying counter that only sounds above a certain threshold of new detections, on a cooldown. With a cooldown between 0.5-1s the number of pings would tell how big of a radar signature is appearing. Only one audio file needed.
OnIntelChange
DetectionCounter = DetectionCounter + 1
end
RadarPingBeat
If DetectionCounter > someThreshold and cooldown:IsExpired() then
PlayPing()
cooldown:Start()
end
DetectionCounter = DetectionCounter * 0.85
end
Not wild about a location based ping, both from a game design standpoint and for the technical overhead it would entail (how do you group the radar blips?).
(And any signal is just another thing you can use to distract your opponent.)