If you want different voices, you will have to use some Javascript API like https://responsivevoice.org/api/ in your custom plugin.
If you are OK with just plain voice alerts, you can use HTML5 speech synthesis APIs as described https://developers.google.com/web/updates/2014/01/Web-apps-that-talk-Introduction-to-the-Speech-Synthesis-API in your custom plugin.
Both of these require you to have some knowledge of Javascript.