Increase Asterisk 16 audio quality

Hello, I am using Issabel 4 with asterisk 16. At the moment I can only upload audio file at 8000 hz . I would like to know if it's possible to use .wav files at an higher rates like 16000 hz or 48000 hz in order to increase audio quality.
Audio files should be used for all the audio parts: IVR, Announcements etc...