Php 文本到语音：不考虑音高值

我正在用php调用Google Text to Speech的rest API.

我是这样打电话的:

    $url = "https://texttospeech.googleapis.com/v1/text:synthesize?key=".$key;

    $data = array(
                    'input' => array(
                        'ssml' => $testo
                    ),
                    'voice' => array(
                        "languageCode" => "en-us",
                        "name" => "en-US-Wavenet-I",
                        "ssmlGender" => "MALE"
                    ),
                    'audioConfig' => array(
                        'audioEncoding' => "LINEAR16",
                        "effectsProfileId" =>  [
                          "small-bluetooth-speaker-class-device"
                        ],
                        "speakingRate" => 1,
                        "pitch" => 4,
                     )
              );

    $options = array(
        'http' => array(
                    'header' => "Content-Type: application/json\r\n",
                    'method' => 'POST',
                    'content' => json_encode($data)
                )
            );

            $context = stream_context_create($options);
            $response = file_get_contents($url, false, $context);
          
            if ($response === false) {
                
            } else {
            
                $response_data = json_decode($response, true);
                ......
            }

这种回应似乎忽略了音调的价值.我既try 将其作为整数传递，也try 将其作为字符串传递，但结果不变. 我做错了什么？

谢谢.