An important consideration in the process of file encoding is the quality of the final product. The encoding type called MPEG Layer-3 allows for size reduction with minimum loss in quality.
For a sound file with voice only you can make selections as shown below.
For file Format select "MPEG Layer-3"
For Attributes select 32kBit/s, 22,050 Hz, Mono
Click "OK" then select "Save" file.
It's True!
Your newly optimized "test1optimized.wav" file is now about 1/8 to 1/10 of it's original size.