Look up the free program audacity,you can record your voice and use effects to boost volume change pitch ect,when your done save as wav and upload as sound file,remember you can only upload to a max of 10 seconds in length.
that gets you a sound file when you got that via inventory goto create and new gesture,add the sound you created plus any text you want and use waits of different lengths to get the sound and text matched up and your done.