Hello DD@SD,
Thanks for posting in the Apple Support Communities. We're happy to look into this with you. We're not exactly sure what you mean by "boing sound". Could you explain this in more detail?
In the meantime, have you tried adjusting your Siri options, to see if changing the Siri voice or how Siri responds might help? Change Siri settings on iPhone - Apple Support
Change the voice for Siri
You can change the Siri voice (not available for all languages).
1. Go to Settings
> Siri & Search.
2. Tap Siri Voice, then choose a different variety or voice.
Change how Siri responds
Siri can respond out loud or silently (with text onscreen). You can also see your request onscreen.
Go to Settings
> Siri & Search, then do any of the following:
- Change when Siri provides voice responses: Tap Siri Responses, then choose an option below Spoken Responses.
- Always see the response from Siri onscreen: Tap Siri Responses, then turn on Always Show Siri Captions.
- See your request onscreen: Tap Siri Responses, then turn on Always Show Speech.
Best regards.