Why can't I hear anything in firefox (SpeechSynthesisUtterance)?

Question

JavaScript

I try SpeechSynthesisUtterance
In chrome it works correctly, in firefox it shows that it worked, but nothing is heard.

const ssu = new SpeechSynthesisUtterance(text);
  ssu.rate = 0.9;
  ssu.volume = 1;
  ssu.lang = 'ru-RU';
  console.log(window.speechSynthesis, ssu);
  window.speechSynthesis.speak(ssu);

UPD: everything works in Latin ... the problem is most likely that there is no voice in it - there is no Cyrillic.