Not even close. This technique only works when the relative energy of different frequency buckets remains the same, and the same time periods apart (in milliseconds). You are very unlikely to have the same fingerprints when repeating the same words/phrases.

Try using an app that shows the FFT and see if you can get it to show the same thing twice when speaking. For example on Android this works https://play.google.com/store/apps/details?id=org.hermit.aud...