Javascript speechSynthesis.speak和ONED触发之间的显著延迟

你可以在这个演示中看到它。从演讲结束到onEnd触发几乎0.3秒的延迟。是否有解决方法或解决方案

var btn = document.getElementById('btn');
speechSynthesis.cancel()
var u = new SpeechSynthesisUtterance();
u.text = 'This is umer please dont come here';

var  t;
u.onstart = function (event) {
    t = event.timeStamp;
    console.log(t);
};

u.onend = function (event) {
    t = event.timeStamp-t;
    console.log(event.timeStamp);
    console.log((t/1000) +' seconds');
};

btn.onclick = function () {speechSynthesis.speak(u);};