我刚刚遇到了同样的问题，在一个取消后发出一个发言将导致没有发言。
我在**clear（）**调用后添加了一个小的超时（250 ms），它似乎可以工作：

var sayTimeout = null;

function say(text) {
    if (speechSynthesis.speaking) {
        // SpeechSyn is currently speaking, cancel the current utterance(s)
        speechSynthesis.cancel();

        // Make sure we don't create more than one timeout...
        if (sayTimeout !== null)
            clearTimeout(sayTimeout);

        sayTimeout = setTimeout(function () { say(text); }, 250);
    }
    else {
        // Good to go
        var message = new SpeechSynthesisUtterance(text);
        message.lang = "en-US";
        speechSynthesis.speak(message);
    }
}

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它现在似乎工作，使用您提供的代码。

$(document).on("click", "#speak", function() {

  var test = new SpeechSynthesisUtterance("Test");
  window.speechSynthesis.speak(test);
  window.speechSynthesis.cancel();
  var test2 = new SpeechSynthesisUtterance("Test2");
  window.speechSynthesis.speak(test2);

});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div id="speak">CLICK ME TO HEAR TEXT</div>

function texto_a_voz(reproducir, idioma) {

   var synth = window.speechSynthesis;
   var voices = [];
   voices = synth.getVoices();

   var utterThis = new SpeechSynthesisUtterance(reproducir);
   utterThis.voice = voices[idioma];
   utterThis.pitch = pitch.value;
   utterThis.rate = rate.value;

   if (synth.speaking) {
       // SpeechSyn is currently speaking, cancel the current utterance(s)
       synth.cancel();
       setTimeout(function () { synth.speak(utterThis); }, 250);
   }
   else {
       // Good to go
       synth.speak(utterThis);
   }
}

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这段代码直接取自p5speech库的例子。也许这有助于解决这个问题？

function parseResult()
    {
        // recognition system will often append words into phrases.
        // so hack here is to only use the last word:
        var mostrecentword = myRec.resultString.split(' ').pop();
        if(mostrecentword.indexOf("left")!==-1) { dx=-1;dy=0; }
        else if(mostrecentword.indexOf("right")!==-1) { dx=1;dy=0; }
        else if(mostrecentword.indexOf("up")!==-1) { dx=0;dy=-1; }
        else if(mostrecentword.indexOf("down")!==-1) { dx=0;dy=1; }
        else if(mostrecentword.indexOf("clear")!==-1) { background(255); }
        console.log(mostrecentword);
    }

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