There may be browser restrictions preventing autoplaying audio, see this answer
https://stackoverflow.com/questions/53058421/local-variable-audio-in-object-method-not-playing
You can see this in your browser developer tools console, there will be error like this NotAllowedError: The play method is not allowed by the user agent or the platform in the current context, possibly because the user denied permission.
If this sound notification is needed only for some specific users, you can change their browser policy to allow autoplay.