If I want to convert a big size file( 64kpbs or bigger size file WAV FILE) to a smaller size file which is ( 8 to 16 kbps, WAV FILE). How do I convert it?

Bit rate in WAV is number of channels * bit depth * sample rate.

So I presume your current WAV is mono, 8-bit depth, 8000 Hz.

Your request for “8 to 16 kbps” does not make sense. It can only be one bit rate.

The only viable solution is likely to be 16 kbps (mono, 4-bit format, probably ADPCM,with 4000 Hz sample rate). There is no guarantee that the player you intend to play it on will accept it, so you would be better to ask whoever gave you this request exactly what format they want. They may want G.726.

To export a 16 kbps ADPCM WAV:

  1. Set project rate bottom left of Audacity to 4000 Hz (type over the top of the current rate)
  2. If the file is stereo, double-click in the blue waves then use Tracks > Stereo Track to Mono
  3. File > Export… then choose “Other uncompressed files”
  4. Click the “Options…” button.
  5. Set Header to “WAV (Microsoft)”
  6. Set Encoding to “IMA ADPCM” or “Microsoft ADPCM”
  7. OK, type the file name then “Save”.