convertwav.js

cont fs = require('fs');
let wav = new WaveFile(fs.readFileSync(`hello_${username}.wav`));
let wav64 = wav.toBase64()

  axios({
    method: 'POST',
    url: `http://${ROBOT_IP}/api/audio`,
    data:{
      FileName: `hello_${username}.wav`,
      Data: wav64,
      ImmediatelyApply: true, //make Misty play it right away
      OverwriteExisting: true
    }
  }).catch(function(err){
    console.log(err)
  })

say.js

const say = require('say')
say.export(`Hello ${username}`, 'Alex', 0.75, `hello_${username}.wav`, (err) => {
  if (err) {
    return console.error(err)
  }
})