Homeassistant and Browser Sound/Beep

I’m using a conditional card to pop up a webRTC card showing a security camera when a motion is present. I know there’s other ways to do this but it seems simple and works fine. What I’d like to add to this is a ‘beep’ when this happens, so the Alexa Show that I’m running the display on beeps to catch my attention.
My first attempt at a simple way of doing this is by also conditionally opening up an iFrame/Webpage that runs a beep on opening - It’s located in the www folder along with the mp3.

<audio autoplay>
  <source src="/local/Beep-Low.mp3" type="audio/mpeg">
  Your browser does not support the audio element.

This works, but only on the first event. I’m thinking it’s probably as the web page once opened sits open in the background so never ‘re-opens’ when a second event happens. This I think is confirmed as when I alter the web page code to include a refresh every 5 sec, it then continues to beep every 5sec. (If I navigate to a different panel it stops, but then continues when I go back to the panel that has the conditional card on.)

My second attempt was to conditionally use a markdown card which had the same code as above. This opens the media player ok, but for some reason it doesn’t find the mp3 that’s in the /local/ folder?

Is there any way to close an iFrame/webpage once it’s opened, as that would then mean my next re-opening would trigger the ‘autoplay’.
Is there a way of getting the markdown card to see the audio file? (Annoyingy if I put an image in my www folder and add , it finds that)
Has anyone managed to do this in an alternative way? (I’m aware that I could do browser_mod or go with a fully-kiosk arrangement but I think those are a bit complicated for what I need so was hoping for something simple)