The required format of sound file need to 8 Khz sampling rate , 16 bit mono and supported types is wav file
You can use one of following methods to create 8 khz 16 bit mono wav files
a. Microsoft Windows built-in recording tool "Sound Recorder"
1. Click on "start" button on windows operating system.
2. Click on "All Programs"
3. Click on "Accessories"
4. Click on "Entertainment"
5. Click on "Sound Recorder"
6. Record your voice through mic using start and stop buttons
7. Click on File menu
8. Click on "Save as"
9. Enter proper file name
10. Select "Save as type" as wav file
11. Click on "Change" button to change format to 8khz 16 bit mono
12. Upload saved file to Call4Smile as new recording
b. TTS programs like open source espeak, flite and festival and commercial solutions like cepstral, ispeech and voiceforge
c. Open source software audacity for audio recording and editing
d. Professional voice overs from professionals from providers like voice12