Play sound before spoken message on phone

Hi,
I have a working piece of code that plays a spoken message on my smartphone. But I’m always surprised when it is playing, and sometimes I don’t hear the beginning of the message, so I want to play an attention sound before playing the message, but I have no idea how to do this, could someone please advise.

tap_action:
  action: perform-action
  perform_action: notify.mobile_app_kris_nord3
  data:
    message: TTS
    data:
      tts_text: This is a high prio message
      media_stream: alarm_stream
      ttl: 0
      priority: high
  target: {}
name: GSM Kris Text high Prio

Kind Regards
Kris