"en-US-Wavenet-H" and "en-US-Wavenet-G" are not smooth [Google Cloud Text to Speech] - google-text-to-speech

Question

I'm testing Google Cloud Text to Speech. I succeeded in getting the wav audio file, but the sound is not smooth in certain voices, especially "en-US-Wavenet-H" and "en-US-Wavenet-G".
wav file I created(en-US-Wavenet-H, LINEAR16)
Google's demo page(please select "en-US-Wavenet-H")
I used the same json with the demo page. This is my code.
<audio controls="controls" autobuffer="autobuffer" autoplay="autoplay" id="audio">
</audio>
<script type="text/javascript">
var url = 'https://texttospeech.googleapis.com/v1beta1/text:synthesize?key=API_KEY';
var data = `{
"audioConfig": {
"audioEncoding": "LINEAR16",
"pitch": 0,
"speakingRate": 1
},
"input": {
"text": "Google Cloud Text-to-Speech enables developers to synthesize natural-sounding speech with 100+ voices, available in multiple languages and variants. It applies DeepMind’s groundbreaking research in WaveNet and Google’s powerful neural networks to deliver the highest fidelity possible. As an easy-to-use API, you can create lifelike interactions with your users, across many applications and devices."
},
"voice": {
"languageCode": "en-US",
"name": "en-US-Wavenet-H"
}
}`;
var request = new XMLHttpRequest();
request.open('POST', url);
request.onreadystatechange = function () {
if (request.readyState != 4) {
} else if (request.status != 200) {
} else {
var result = request.responseText;
var obj = JSON.parse(result);
document.getElementById("audio").setAttribute('src', 'data:audio/x-wav;base64,' + obj.audioContent);
}
};
request.setRequestHeader('Content-Type', 'application/json; charset=UTF-8');
request.send(data);
</script>
I also tried it with Windows Power Shell & Cloud SDK and the result was the same.
"en-US-Wavenet-I" and "en-US-Wavenet-J" aren't too terrible, but not smooth. Other voices are okay. Why can't I get the same audio as the demo? Thanks in advance.