Puzzling double beep - help please?

I have just started getting some intermittent 'double beeps' or 'double toots' in the car (UK based, Prius Excel 2016 with Touch 2 & Go). If you have heard anything like this, please give me an idea of what might be the cause, so I can stop it!

I have a recording of it here:
Dropbox - Prius Double Beep.m4a

It may be only a coincidence, but it started after I upgraded the Navigation system from the original 2016 version to version 6.11.2WH; and was the first software upgrade I have installed.

There is no visual indication of what the problem is on any display anywhere on the dash or on the navigation head unit. The car is otherwise behaving normally.

It only happens when the car is moving but seems unrelated to the actual speed and so far it seems to be on larger non-residential roads, although that might be a coincidence. The occurrence otherwise appears random. I can get it 2 - 3 times within a minute or just once in 20 - 30 minutes. It has happened at least once on almost every trip over 15 minutes I have made, since the software upgrade.

I have managed to test and eliminate the following as possible causes by checking the status or activating/deactivating each in turn:

1. Low fuel
2. RSA (road sign assist)
3. Lane Sway Warning
4. Lane Departure Alert
5. BSM (blind spot monitor)
6. ICS (Intelligent Clearance Sonar)
7. Park Assist
8. PCS (Pre-Collison System)

Many thanks!

 

Thanks for the swift reply; but not that. On my car, the seat belt and reverse beeps are louder and slightly higher pitched or 'harsher' with a visual display on the dash as well.

The beeps here are sound a little more gentle or less harsh.

 

Thank you very much for responding with these suggestions. I received the same ideas on another forum and someone pointed out this thread which I had forgotten about:
UK owners - speed camera alerts after update? | PriusChat

If you are still interested but cannot hear the audio using the Dropbox link, try downloading the file and playing it (it is only 2 seconds long and only a few kb in size). I will leave it for another month or so before deleting it (unless I can find a way of uploading it permanently on Priuschat - any guidance with this would be much appreciated).

It appears that on one of these earlier map software updates the single pips were changed to these double beeps/pips/toots. Apparently the warnings are also not only for speed cameras, but also traffic light cameras and bus lane cameras. I suspect there are a lot more registered on later versions of the map updates as well, so by updating these maps I now have very many more alerts on my routes.

Congestion in the parts of London that I mostly drive in provide few if any opportunities for speeding or shooting red lights! There are also so many of these cameras that I need to find a way of switching this audible warning off or at least turning the volume down.

At this time, I cannot find anything in the menu system of the central console to make adjustments and cannot find anything in the manual either....