japseye sorry - you're wrong!
First of all - to activate the sound that you point out - you do not need to have running any skin - I have this sound even as a default.
indeed the sound is activated the command line you point out, but the sound can be saved in a folder where I said - that iGO / ui_android / audio / ........ - (where ...... - is exact name audio file - for example. speedcam_off).

And now merits of the case - navi gives you info about the distance to the radar and signals that if the [warning] have it declared - I have so (except the same as you)

approach_beep_distances = 300
warn_distances=150:2000,140:1600,130:1400,120:1200,110:1000,100:800,90:600,80:500,70:400,60:300,50:200,40:100

The first line says about the distance (from the radar) of the signal beep
The second tells you your speed distance warning - that is with your speed 150 km / h stamp radar will appear and you will have a signal at 2000 m from the radar.

Now look at this:
; S P E E D C A M - C A T: 0
[speedcam_category: 0]
activated_spoken_type = speech
activated_speech = "RADAR! Embrace Up!"

approach_beep_distances = 550
approach_beep_spoken_type = sound
approach_beep_speech = "user_alert5"

overspeed_spoken_type = sound; my
overspeed_sound = "speedcam_over_speed"
skin_first_sound = "ovrspon"
skin_speed_sound_delay = 200
skin_repeat_sound = "radar"
skin_repeat_distance = 150
skin_off_sound = "speedcam_off"

As you can see is, and voice and sound - most importantly, it works without problems.
Sound files I placed where I wrote - iGO / ui_android / audio.
If you do not have an audio folder is set up and move it to the custom sound files.

And now think: You're on your side of the road radar - but not directed towards you, but the opposite - the radar is a type of two-sided. You ride you pass it you speedcam_off signal and then get home pic with your photo and mandate.
Why - because the radar was two-sided and therefore declare the trigger signal line speedcam_off - without declaring the distance at which the signal is activated is a mistake that can cost you.
For me, this signal is activated only 300 m for radar

That's it.
PS thank you button is on the left below the post (postage small hand)
greet and watch out for seats - in the UK you have a much more "inferior" types of radars than I do in Poland.
Regards wojpen