const options = {
  method: 'POST',
  headers: {
    Authorization: 'Bearer <token>',
    'Content-Type': 'application/json'
  },
  body: '{
    "voice_id":"<string>",
    "text":"<string>",
    "sample_rate":8000,
    "add_wav_header":true}'
  };

fetch('https://waves-api.smallest.ai/api/v1/lightning/get_speech',
   options)
  .then(response => response.json())
  .then(response => console.log(response))
  .catch(err => console.error(err));